Maybe this is wrong, but my understanding is BTRFS is generally slower than EXT4, and that's okay. It's not going for speed

Where it shines is not in its speed but in its versatility offering compression, rollback, subvol, etc

For example, for applications, you do a lot of writes/reads to Documents or load resources like for games, so use EXT4 for /home or for a dedicated /games partition

For your system, it could be broken via config tweaks or updates, so use BTRFS to have the rollback options