I think you're going to get a wide variety of responses here. It comes down to a lot of factors.

For me personally, I've been shifting everything I have to Btrfs, so I can tell you what I've done recently and why.

A big caveat is that many of my systems have multiple physical drives. This means I'm often setting things up based on the speed and capacity of those disks.

But, I do have one system with a single drive shared for booting, root, and home. It's set up like this:

1. A FAT32 partition for /boot. 512 MB.

2. A single Btrfs partition across the rest of the drive.

3. Btrfs subvolumes: @ mounted at /, @home mounted at /home. @snapshots mounted at /.snapshots.

I could go crazy with other subvols (e.g. for /var/log), but ultimately it is sufficient for me to be able to snapshot / and /home separately.

For some of my other systems, I'll have / and /home on different drives. In that case, each has their own @snapshots with their own mount point. I tend still to throw the EFI boot partition mounted at /boot on the same drive as /.

It's very easy to simply change /etc/fstab as needed and point to another snapshot, effectively rolling back the drive to some former point as necessary.