I'm currently running the 64bit build of alpine. I've read some conflicting benchmarks about if 64bit or 32bit is faster, but I think I'm inclined to feel that 64bit is similar, but slightly better in a few specific workloads. (While using more ram most of the time).

black borders

doas nvim /boot/usercfg.txt
disable_overscan=1

audio

doas nvim /boot/usercfg.txt
dtparam=audio=on

opengl

doas nvim /boot/config.txt
dtoverlay=vc4-kms-v3d

apk add mesa-egl