BTRFS doesn't care how big the disks are and you can just tell it to keep x number of copies of each data / metadata / system block and it will do the work of keeping your copies on different devices across the file system. Much like SHR, performance isn't linear with different sized devices, but it's super simple to setup and in tree where ZFS has a lot more complexity and is not baked into the kernel.

Snapshots are available, but a little more work to deal with since you have to learn about subvolumes. It's not that hard.

Edit: TIL, SHR is just mdadm + btrfs.