@a1ba btrfs have a good features set, but it very slow (if features used), and allocations arch ruining most of features, for example if de-duplication is used, you will end up with enospc with 10-30% of space used, and you will need to run btrfs balance start -dusage=50 in infinite loop.

i am testing bcachefs on few non-critical installations right now, it have comparable to btrfs set of useful features (lacking de-duplication is important but not critical for me), also bcachefs have background recompression which is looks extremely useful on glance ....