[Samsung Galaxy S21 Ultra] edmondt:
I'm just going to attach the one that I'm currently using, maybe it's just my placebo; but I think it made everything better.

Add inside /system/build.prop

#----------------------------------
# Start
#----------------------------------

# Audio enhancer

persist.audio.fluence.mode=endfire
persist.audio.vr.enable=true
persist.audio.handset.mic=digital
af.resampler.quality=255
mpq.audio.decode=true

#----------------------------------

# Call delay

ro.telephony.call_ring.delay=800

#----------------------------------

# Video acceleration enabled

video.accelerate.hw=1

#----------------------------------

# Wifi scaning rate [every 60 --> 1 scan / min]

wifi.supplicant_scan_interval=180

#----------------------------------

# Deeper sleep/better battery life [for extrimmly power save] [kills all background apps]

ro.ril.disable.power.collapse=1
# pm.sleep_mode=1

#----------------------------------

# Improves audio and video recording quality

ro.media.enc.hprof.vid.fps=65
ro.media.enc.hprof.vid.bps=8000000

ro.media.capture.maxres=8m
ro.camcorder.videoModes=true

#----------------------------------

# Picture Quality Enhancer

ro.media.enc.jpeg.quality=100
ro.media.dec.jpeg.memcap=8000000

#----------------------------------

# Disable Boot Animation [for Enable set 0]

debug.sf.nobootanimation=1

#----------------------------------

# Disable Camera Sound

ro.camera.sound.forced=0

#----------------------------------

# Better Scrolling

ro.min_pointer_dur=8
ro.max.fling_velocity=12000
windowsmgr.max_events_per_sec=60

#----------------------------------

# Disable strict mode checking

persist.android.strictmode=0

#----------------------------------

# Remain launcher in memory
ro.HOME_APP_ADJ=1

#----------------------------------

# Disable usb debugging popup in notification

# persist.adb.notify=0

#----------------------------------

# Proximeter delays

ro.lge.proximity.delay=25
mot.proximity.delay=10

#----------------------------------

# media enhancer [codecs]

ro.media.dec.aud.flac.enabled=1
ro.media.dec.aud.wma.enabled=1
ro.media.dec.vid.avi.enabled=1
ro.media.dec.vid.wmv.enabled=1
ro.media.dec.aud.wma.enabled=1
ro.media.dec.aud.mp3.enabled=1
ro.media.dec.vid.mp4.enabled=1
ro.media.dec.aud.flac.enabled=1
ro.media.dec.vid.H.264.enabled=1
ro.media.enc.aud.flac.enabled=1
ro.media.enc.vid.H.264.enabled=1
ro.media.enc.aud.wma.enabled=1
ro.media.enc.vid.wmv.enabled=1
ro.media.enc.aud.mp3.enabled=1
ro.media.enc.vid.mp4.enabled=1

#----------------------------------

# Improved performance

debug.performance.tuning=1

#----------------------------------

# DNS Servers [Quad9 & Cloudflare]

net.dns1=9.9.9.9
net.dns2=149.112.112.112
net.dns3=1.1.1.1
net.dns4=1.0.0.1

net.wlan0.dns1=9.9.9.9
net.wlan0.dns2=149.112.112.112
net.wlan0.dns3=1.1.1.1
net.wlan0.dns4=1.0.0.1

net.eth0.dns1=9.9.9.9
net.eth0.dns2=149.112.112.112
net.eth0.dns3=1.1.1.1
net.eth0.dns4=1.0.0.1

net.wcdma.dns1=9.9.9.9
net.wcdma.dns2=149.112.112.112
net.wcdma.dns3=1.1.1.1
net.wcdma.dns4=1.0.0.1

net.hspa.dns1=9.9.9.9
net.hspa.dns2=149.112.112.112
net.hspa.dns3=1.1.1.1
net.hspa.dns4=1.0.0.1

net.lte.dns1=9.9.9.9
net.lte.dns2=149.112.112.112
net.lte.dns3=1.1.1.1
net.lte.dns4=1.0.0.1

net.ltea.dns1=9.9.9.9
net.ltea.dns2=149.112.112.112
net.ltea.dns3=1.1.1.1
net.ltea.dns4=1.0.0.1

#----------------------------------

# Better Network Signals

persist.cust.tel.eons=1
ro.config.hw_fast_dormancy=1

#----------------------------------

# Better call voice quality

ro.ril.enable.amr.wideband=1

#----------------------------------

# Faster streaming videos

media.stagefright.enable-player=true
media.stagefright.enable-meta=true
media.stagefright.enable-scan=true
media.stagefright.enable-http=true
media.stagefright.enable-rtsp=true
media.stagefright.enable-record=false

#----------------------------------

# Disables built in error reporting

profiler.force_disable_err_rpt=1
profiler.force_disable_ulog=1

#----------------------------------

# Disables kernel error checking

ro.kernel.android.checkjni=0
ro.kernel.checkjni=0

#----------------------------------

# Disable Logcat

logcat.live=disable

#----------------------------------

# Disables sending of usage data

ro.config.nocheckin=1

#----------------------------------

# Boost Booting Speed & hibernate mode

ro.config.hw_quickpoweron=true
persist.sys.shutdown.mode=hibernate

#----------------------------------

# Very fast reboot

persist.sys.purgeable_assets=1

#----------------------------------

# Disables locating

ro.com.google.locationfeatures=0
ro.com.google.networklocation=0

#----------------------------------

# Net speed enhancer[tcp buffersize]

net.tcp.buffersize.default=6144,87380,110208,6144,16384,110208
net.tcp.buffersize.edge=6144,26280,35040,6144,16384,35040
net.tcp.buffersize.evdo_b=6144,262144,1048576,6144,262144,1048576
net.tcp.buffersize.gprs=6144,8760,11680,6144,8760,11680
net.tcp.buffersize.hsdpa=6144,262144,1048576,6144,262144,1048576
net.tcp.buffersize.hspa=6144,87380,262144,6144,16384,262144
net.tcp.buffersize.lte=262144,524288,3145728,262144,524288,3145728
net.tcp.buffersize.umts=6144,87380,110208,6144,16384,110208
net.tcp.buffersize.wifi=262144,524288,1048576,262144,524288,1048576

#----------------------------------

# For Sensor Sleep Control
ro.ril.sensor.sleep.control=1

#----------------------------------

# DHA tunning
ro.config.dha_tunnable=1

#----------------------------------

# Faster Boot-Animation FPS
# boot.fps=20

#----------------------------------
# END
#----------------------------------

##CUSTOM TWEAKS##
fw.max_users=3
fw.power_user_switcher=1
fw.show_hidden_users=1
fw.show_multiuserui=1
ring.delay=0
ro.kernel.android.checkjni=0
ro.kernel.checkjni=0
ro.media.enc.jpeg.quality=100
ro.securestorage.support=false
ro.telephony.call_ring.delay=0
wlan.wfd.hdcp=disable
ro.security.vaultkeeper.native=0
ro.config.hw_quickpoweron=true
profiler.force_disable_err_rpt=1
profiler.force_disable_ulog=1
wifi.supplicant_scan_interval=120
debug.performance.tuning=1
ro.HOME_APP_ADJ=1
ro.lge.proximity.delay=25
mot.proximity.delay=25
ro.ril.power_collapse=1
pm.sleep_mode=1
persist.cust.tel.eons=1
persist.adb.notify=0
persist.service.adb.enable=1
ro.config.tima=0
ro.boot.flash.locked=1
ro.security.vaultkeeper.feature=0
ro.security.vaultkeeper.native=0

ro.HOME_APP_ADJ = 1

debug.performance.tuning=1
ro.ril.power_collapse=1
ro.ril.disable.power.collapse=0
pm.sleep_mode=1
ro.config.hw_power_saving=true
persist.cust.tel.eons=1
ro.ril.enable.amr.wideband=1
ro.config.hw_fast_dormancy=1
ro.config.vc_call_steps=20
ro.config.hw_power_saving=1

ro.ril.hep=0
ro.ril.hsxpa=2
ro.ril.gprsclass=12
ro.ril.enable.dtm=1
ro.ril.hsdpa.category=8
ro.ril.enable.a53=1
ro.ril.enable.3g.prefix=1
ro.ril.htcmaskw1.bitmask=4294967295
ro.ril.htcmaskw1=14449
ro.ril.hsupa.category=6

#GOOGLE DNS*

net.dns1=8.8.8.8
net.dns2=8.8.4.4
net.wcdma.dns1=8.8.8.8
net.wcdma.dns2=8.8.4.4
net.hspa.dns1=8.8.8.8
net.hspa.dns2=8.8.4.4
net.lte.dns1=8.8.8.8
net.lte.dns2=8.8.4.4
net.ltea.dns1=8.8.8.8
net.ltea.dns2=8.8.4.4
net.rmnet0.dns1=8.8.8.8
net.rmnet0.dns2=8.8.4.4
net.gprs.dns1=8.8.8.8
net.gprs.dns2=8.8.4.4
net.ppp0.dns1=8.8.8.8
net.ppp0.dns2=8.8.4.4
net.wlan0.dns1=8.8.8.8
net.wlan0.dns2=8.8.4.4
net.eth0.dns1=8.8.8.8
net.eth0.dns2=8.8.4.4

wifi.supplicant_scan_interval=300

# Net speed tweak
net.tcp.buffersize.default=4096,87380,256960,4096, 16384,256960
net.tcp.buffersize.wifi=4096,87380,256960,4096,163 84,256960
net.tcp.buffersize.edge=4096,87380,256960,4096,163 84,256960
net.tcp.buffersize.hspa=4096,87380,256960,4096,163 84,256960
net.tcp.buffersize.hspda=4096,87380,256960,4096,16 384,256960
net.tcp.buffersize.gprs=4096,87380,256960,4096,163 84,256960
net.tcp.buffersize.umts=4096,87380,256960,4096,163 84,256960
net.tcp.buffersize.hsdpa=6144,87380,1048576,6144,8 7380,1048576
net.tcp.buffersize.hspap=4096,87380,1220608,4096,1 6384,393216
net.tcp.buffersize.hsupa=4096,87380,704512,4096,16 384,262144
net.tcp.buffersize.evdo=4096,87380,563200,4096,163 84,262144
net.tcp.buffersize.evdo_b=6144,87380,1048576,6144, 87380,1048576
net.tcp.buffersize.lte=524288,1048576,2097152,5242 88,1048576,2097152

ro.lge.proximity.delay=0
mot.proximity.delay=25

ro.telephony.call_ring.delay=0
ring.delay=0

ro.media.enc.jpeg.quality=100
ro.media.dec.jpeg.memcap=8000000
ro.media.enc.hprof.vid.bps=8000000
ro.media.capture.maxres=8m
ro.camcorder.videoModes=true

ime_vibration_pattern=0:60
ro.media.capture.flash=led
ro.media.capture.flashMinV=3300000
ro.media.capture.torchIntensity=40
ro.media.capture.flashIntensity=70
ro.media.capture.fast.fps=4
ro.media.capture.slow.fps=120
ro.camcorder.videoModes=true
ro.media.enc.hprof.vid.fps=65

# Video streaming optimization
media.stagefright.enable-player=true
media.stagefright.enable-meta=true
media.stagefright.enable-scan=true
media.stagefright.enable-http=true
media.stagefright.enable-record=false
media.stagefright.enable-rtsp=true
media.stagefright.enable-qcp=true
media.stagefright.enable-aac=true

# Camera Tweaks Supports Google Camera
persist.camera.HAL3.enabled=1
camera.HAL3.enabled=1
persist.camera.eis.enable=1
camera.eis.enable=1
persist.camera.is_mode=4
camera.is_mode=4
persist.camera.disable_zsl_mode=1
camera.disable_zsl_mode=1
persist.camera.gyro.android=4
camera.gyro.android=4
persist.camera.tof.direct=1
camera.tof.direct=1
persist.camera.tnr.preview=1
camera.tnr.preview=1
persist.camera.tnr.video=1
camera.tnr.video=1
ro.camera.notify_nfc=1
camera.notify_nfc=1

ro.media.panorama.defres=3264x1840
ro.media.panorama.frameres=1280x720

logcat.live=disable

# Auto Dimming Issues
persist.sys.cabc.enable=0
ro.service.cabc.supported=false

#scrolling speed
windowsmgr.max_events_per_sec=150
ro.min_pointer_dur=8
ro.max.fling_velocity=12000
ro.min.fling_velocity=8000
persist.sys.scrollingcache=3
debug.sf.hw=1