Its multithreaded performance is still ass compared to XFS, which solved its small file problems a long time ago so it basically does everything you need

fs shrinking is insane, nobody should use that. If you're stuck in a position where you *need* to shrink an fs you did something very very wrong and you should be punished for not planning better or owning more hardware to alleviate your issue

BTRFS is also CoW and it's not super useful to compare CoW filesystem so log/journal filesystems as they have very different use cases. e.g., putting a database on a CoW is really dumb and you'll just suffer the write amplification penalty