[OnePlus 3 Guides, News, & Discussion] GuestK00458:
I have made a little script to remove some stuff after flashing and it seems this is doing the job, though performance is still dropping, even with modified /system/init.environ.rc.

Since I have limited Android background knowledge, I have no idea where to search to get an idea where the performance drop is coming from.

This is the script:

# First mount firmware_mnt
mount /dev/block/by-name/modem /system/system/vendor/firmware_mnt

# Remove all files with ifaa, soter and alipay
bloblist="
/system/system/framework/arm/boot-org.ifaa.android.manager.art
/system/system/framework/arm/boot-org.ifaa.android.manager.oat
/system/system/framework/arm/boot-org.ifaa.android.manager.vdex
/system/system/framework/arm64/boot-org.ifaa.android.manager.art
/system/system/framework/arm64/boot-org.ifaa.android.manager.oat
/system/system/framework/arm64/boot-org.ifaa.android.manager.vdex
/system/system/framework/boot-org.ifaa.android.manager.vdex
/system/system/framework/org.ifaa.android.manager.jar
/system/system/lib64/vendor.oneplus.hardware.ifaa@2.0.so
/system/system/vendor/bin/hw/vendor.oneplus.hardware.ifaa@2.0-service
/system/system/vendor/bin/hw/vendor.qti.hardware.soter@1.0-service
/system/system/vendor/etc/init/vendor.oneplus.hardware.ifaa@2.0-service.rc
/system/system/vendor/etc/init/vendor.qti.hardware.soter@1.0-service.rc
/system/system/vendor/firmware_mnt/image/alipay.b00
/system/system/vendor/firmware_mnt/image/alipay.b01
/system/system/vendor/firmware_mnt/image/alipay.b02
/system/system/vendor/firmware_mnt/image/alipay.b03
/system/system/vendor/firmware_mnt/image/alipay.b04
/system/system/vendor/firmware_mnt/image/alipay.b05
/system/system/vendor/firmware_mnt/image/alipay.b06
/system/system/vendor/firmware_mnt/image/alipay.mdt
/system/system/vendor/firmware_mnt/image/soter64.b00
/system/system/vendor/firmware_mnt/image/soter64.b01
/system/system/vendor/firmware_mnt/image/soter64.b02
/system/system/vendor/firmware_mnt/image/soter64.b03
/system/system/vendor/firmware_mnt/image/soter64.b04
/system/system/vendor/firmware_mnt/image/soter64.b05
/system/system/vendor/firmware_mnt/image/soter64.b06
/system/system/vendor/firmware_mnt/image/soter64.mdt
/system/system/vendor/lib64/hw/vendor.qti.hardware.soter@1.0-impl.so
/system/system/vendor/lib64/vendor.qti.hardware.soter@1.0.so
"

for blobname in $bloblist
do
if [ -d "$blobname" ]; then
chmod -R 777 "$blobname" 2>/dev/null
rm -rf "${blobname:?}"/* 2>/dev/null
else
chmod 777 "$blobname" 2>/dev/null
rm -f "$blobname" 2>/dev/null
fi
done

# Remove org.ifaa.android.manager.jar from environ.rc
sed -i 's/:\/system\/framework\/org.ifaa.android.manager.jar//' /system/init.environ.rc

umount /system/system/vendor/firmware_mnt

And this is init.environ.rc after using sed (org.ifaa.android.manager.jar removed):

# set up the global environment
on early-init
export ANDROID_BOOTLOGO 1
export ANDROID_ROOT /system
export ANDROID_ASSETS /system/app
export ANDROID_DATA /data
export ANDROID_STORAGE /storage
export ANDROID_RUNTIME_ROOT /apex/com.android.runtime
export ANDROID_TZDATA_ROOT /apex/com.android.tzdata
export EXTERNAL_STORAGE /sdcard
export ASEC_MOUNTPOINT /mnt/asec
export BOOTCLASSPATH /apex/com.android.runtime/javalib/core-oj.jar:/apex/com.android.runtime/javalib/core-libart.jar:/apex/com.android.runtime/javalib/okhttp.jar:/apex/com.android.runtime/javalib/bouncycastle.jar:/apex/com.android.runtime/javalib/apache-xml.jar:/system/framework/framework.jar:/system/framework/ext.jar:/system/framework/telephony-common.jar:/system/framework/voip-common.jar:/system/framework/ims-common.jar:/system/framework/android.test.base.jar:/system/framework/telephony-ext.jar:/system/framework/WfdCommon.jar:/apex/com.android.conscrypt/javalib/conscrypt.jar:/apex/com.android.media/javalib/updatable-media.jar
export DEX2OATBOOTCLASSPATH /apex/com.android.runtime/javalib/core-oj.jar:/apex/com.android.runtime/javalib/core-libart.jar:/apex/com.android.runtime/javalib/okhttp.jar:/apex/com.android.runtime/javalib/bouncycastle.jar:/apex/com.android.runtime/javalib/apache-xml.jar:/system/framework/framework.jar:/system/framework/ext.jar:/system/framework/telephony-common.jar:/system/framework/voip-common.jar:/system/framework/ims-common.jar:/system/framework/android.test.base.jar:/system/framework/telephony-ext.jar:/system/framework/WfdCommon.jar
export SYSTEMSERVERCLASSPATH /system/framework/org.lineageos.platform.jar:/system/framework/services.jar:/system/framework/ethernet-service.jar:/system/framework/wifi-service.jar:/system/framework/com.android.location.provider.jar

I have not used find because I had some issues in the past with find in combination of double astrix (*string*), though searching through /system after boot does not give any positive results on soter, alipay or ifaa so all seems removed. Have the feeling though, somewhere 'things' are linked to removed stuff which is the reason for the performance drop.