Oh nah, I wasn't getting any drain. I meant my battery was running out normally.
When installing Viper I actually don't remember getting the quality choices. Just a prompt to install drivers and that's it. In the past though, I always picked High.
But anyway, the same user who linked that Deuteronomy build told me try Vioer4Android FX 2.6.0.4. Got it and tested. It works much better.
Wiped out and restored the ROM. Installed the apk. It told me something about a fingerprint id problem. It also prompted for root (the others did not).
Rebooted phone. Had a temporary SuperSU hiccup where it wanted to update the binary. Failed at first but luckily I keep the apk on hand. Reinstalled it and it successfully updated the binary.
After reboot I ran Viper again. Driver installation has only one prompt with two choices, 2.5.0.4 (recommended) or 2.3.something (sorry, forgot).
Reboot once again.
Using Retro Music player on AEX, Viper was processing. Skipped from track to track with processing still good throughout. Stopping playback for a bit and then resuming, still good.
Stopped and exited player. Restart and play, processing did not resume. Had to close and restart Viper.
Short test but still much better than previous attempts.
https://labs.xda-developers.com/store/app/com.pittvandewitt.viperfx
ZTE Axon 7 A2017U, AospExtended v5.4 ROM, HELLSGATE Kernel, Multiboot, Tapatalk 4.9.3