Can I add storage pool type X after lxd init has been ran?

Hi all,
we ran our lxd ini long time ago. The servers config has changed since that time and a few features have been added to it.
Our storage pool so far has been ext4-based but we would like to add storage pool(s) based on xfs/zfs/btrfs - can we do that later on ?

Yes that is fine, use lxc storage create.