Android 15 has been refactored to support using 16 KB page sizes, and file systems like EROFS and F2FS have been made compatible.
A page is the granularity at which an operating system manages memory. Most CPUs today support a 4 KB page size and so the Android OS and applications have historically been built and optimized to run with a 4 KB page size. ARM CPUs support the larger 16 KB page size. When Android uses this larger page size, we observe an overall performance boost of 5-10% while using ~9% additional memory.
In order to improve the operating system performance overall and to give device manufacturers an option to make this trade-off, Android 15 can run with 4 KB or 16 KB page sizes.
The very first 16 KB enabled Android system will be made available on select devices as a developer option. This is so you can use the developer option to test and fix (if needed) your applications to prepare for Android devices with 16 KB page sizes in the near future.
I used to use VLC for music, but these days I use Symphony to play local files on my phone. VLC tended to struggle when scanning or indexing large folders (which it did all the time...), while Symphony is a bit better at that. That said, I still use VLC for video and for casting things from my DLNA server (VLC supports Chromecast).
For ebooks, I've used Librera FD and that has been mostly OK. I'll checkout the two you mentioned though. Thanks!