Okay I just tried uninstalling and reinstalling 948 with no altered settings at all, just the way it comes right out of the box, not even activated to the full version, just to be sure it wasn't any of my settings. With that particular file, if you set RG preamp to > +11 and mess with the "Replay Gain" setting, you will see that it quickly becomes non-functional, staying at the same gain whether replay gain is turned on or off. < +11 works fine. The level this starts to happen at with other files seems to vary depending on some combination of track gain, OPUS header gain, and RG preamp that's more complex than just being a total of > 16 that I'm sick of trying to pick out by ear depending on the file, and quantify without any debug output.
For FLAC and MP3 files I've always just scanned for replay gain with Foobar, and then set Poweramp to Apply Gain + prevent clipping. With the rg preamp all the way up it fixed the issue of the scanner wanting to normalize everything to like -12db , without ending up clipping or needing a huge gain overlap elsewhere in the signal chain. I guess I can't do the same thing with OPUS anyways because it doesn't support a peak tag, but the scanner seems to take clipping into account for OPUS headers. I don't actively mess with the rg preamp setting, so I can just have the scanner put the gain I want in the OPUS header, and remove their track gains completely. That way all my old MP3s will get normalized by replay gain, and the OPUS files by the header gain. The way Poweramp handles OPUS + RG doesn't seem right regardless, but I guess it doesn't really matter if I can work around it. Otherwise, I still haven't found another Android player that I like as much, except for this issue, and it remains damn near the only Android app I have ever liked enough to pay for. Thanks for all the hard work.