The main benefits to BTRFS over something like ext4 tends to be considered as; the subvolume support - which is what’s used for snapshotting, the granluar quotas, reflinks, transparent compression, and the fact that basically all filesystem operations can be performed online.

I’m personally running BTRFS in a couple of places; NAS, laptop, and desktops. Mainly for the support to do things like snapshots and subvolumes, but I also make heavy use of both reflinks and compression, and I’ve also made use of online filesystem actions quite a few times.

Using btrfs makes a lot if sense on a NAS, because it allows you to make snapshots in a nice way. It also has some features that give your data better odds of survival if something goes wrong.

If you have steam, btrfs compression will dramatically shrink the size of an installed game with zero performance impact. In some cases, the disk read speed even increases.

non system disk

That really depends on what you mean by that? Is it an internal or external drive, what sort of drive is it (HDD, SSD etc), and what are you going to use it for, and are you planning to share the drive with other operating systems?

Because while btrfs is nice in general, you may find other filesystems more suitable, depending on your usage requirements.

I like BTRFS’s checksumming abilities and compression the most. BTRFS will keep track of every block of data’s checksum, and when you run a scrub it will detect bitrot. If you want to heal the bitrot you’ll need to run e.g. RAID1. RAID5/6 are not stable so don’t use those. ZSTD:1 compression is basically free storage with no downside, and can massively speed up file operations if you’re using spinning rust.

Personally I run BTRFS on any disk that only needs a single drive, like OS disk or games drive. My NAS runs a ZFS array for any mass storage, which includes basically the same feature set as BTRFS, except RAID actually works and everything is a tiny bit better. A ZFS NAS isn’t very good unless you pump a decent amount of money into it to get it going, so if you’re on a tight budget I’d recommend MergerFS+SnapRAID backed by BTRFS disks, which is very similar to Unraid in terms of storage paradigm except free.

I’d say it’s essential on a SMR drive

I use Btrfs on my secondary drives as well, just for the checksumming capabilities. If there is data errors, I would like to know about it (even if I cannot do anything about it, because I do not have redundancy set up). I have my fstab set up so that it mounts with noatime,compress-force=zstd:1

Performance-wise, Btrfs has been improving a lot even in just the past few years. I think if I were using a very weak computer (like raspberry pi 1 strength) I would not use Btrfs or a CoW fs.

I usually just stick to the standard file system to any OS.

So for Linux that would be ext4.

For external drives i use either FAT32 (the ol’ reliable) or exFAT (the fastest for dealing with large files when you set the max allocation unit size AKA 32MB).