FLACs from CDs, deemix-gui, qobuz-dl, and Soulseek. 102,000 songs. Play at home with Logitech Media Server. On the road I’ve transcoded it all to 128kbps Opus so i can fit it on a microsd card and I play it with PowerAmp. I mostly use Blessing2 Dusk earbuds with a Shanling MW200 bluetooth neckband, but sometimes also I use Focal Clear OG open-back over-ear cans with a qdelix 5k for bluetooth.
Yeah you don’t want the battery to sit at 100% or 0%. I just bulged out my 10 yr old work macbook battery by leaving it plugged in, not the first one i’ve seen either. There are utils that can set charge limits in linux https://askubuntu.com/questions/34452/how-can-i-limit-battery-charging-to-80-capacity
TBH you MBP battery is probably nearing EOL but it may actually be replaceable.