[OnePlus 5T  Questions & Answers] ClinicalTrack:
For a while now I've been asking about some of these and searching online, but no one seems to know too many details about these apps. Recently I decided to dive deep and find out.

In the latest 5.0.3 build for the 5T, I see 7 apps in /system/vendor/app/

/system/vendor/app/aptxui/aptxui.apk

This one appears to be a codec manager for bluetooth audio settings. In another thread someone pointed out it has annoying popup notifications. The entire apk could be deleted if it's annoying enough.

/system/vendor/app/CABLService/CABLService.apk

Inside the app is /res/values/strings.xml which shows CABL stands for "Content Adaptive Backlight Settings", for which the backlight can be automatically adjusted based on the screen content. It says, "Lower quality level indicate CABL will try to save as much power as possible without significantly affecting content being displayed. Auto visual quality level means CABL will try to maximize power savings based on auto detecting type of content being displayed."

/system/vendor/app/colorservice/colorservice.apk

This apk "Allows the application to directly affect the device's display paramter" and calls native_getAdaptiveBacklightScale, native_getBacklightQualityLevel, and native_getColorBalance. I believe it changes the screen color balance at sunrise and sunset. The way it's written seems insanely over-complicated.

/system/vendor/app/Perfdump/Perfdump.apk

Perfdump is a "Performance Tool by Qualcomm" which allows devs to grab details of the system (device storage, external storage, hardware test, logs) into a compiled report. The inclusion of <action android:name="android.provider.Telephony.SECRET_CODE"/> does seem odd though.

The full list of report objectives includes: Graphics, Input, View System, WebView, Window Manager, Activity Manager, Sync Manager, Audio, Video, Camera, HAL, Application, Resource Loading, Dalvik VM, RenderScript, Bionic C Library, Power Management, Package Manager, System Server, Database, CPU Scheduling, CPU Frequency, CPU Idle, CPU Load, Memory Reclaim, Binder Driver, Binder Lock, Synchronization, Workqueues, Regulators, Page Cache, IRQ Events, Disk I/O, MDSS, GPU, Screen Capture, and Overlay Alpha Setting.

/system/vendor/app/SecProtect/SecProtect.apk

SecProtect allows users or devs to encrypt or decrypt files. "Please set password first before encrypting/decrypting. You need to provide this password for decrypting the encrypted file later." What is being encrypted? No idea. XML tools include:

change_password_layout.xml

create_password_layout.xml

encryptdata.xml

encryptdata_operation.xml

file_explorer.xml

list_item_authaccess_settings.xml

/system/vendor/app/SVIService/SVIService.apk

SVI Display Settings can "Enhance the viewing based on the ambient condition", it's some sort of automatic screen brightness adjustment tool. The line ".method public abstract unlinkToDeath(Landroid/os/IHwBinder$DeathRecipient)Z" is a little disturbing.

/system/vendor/app/TimeService/TimeService.apk

TimeServiceBroadcastReceiver uses action.TIME_SET and action.DATE_CHANGED to maintain the correct time and date on Android devices. There are only a few lines of code in here, and no NTP servers listed, it's difficult to see how it works.