I am going to be running lxd to mess around on a really low storage laptop is directory backed the right choice If I want them both to share storage space for example if delete a container I gain back storage to install something else?
I use LXD on a Raspberry Pi3 with a 32 Go Sdcard and 1 Go Ram with a Btrfs storage and it works for me. Dir storage has limitations especially with snapshots, it’s to be avoided unless really necessary.
How much is your free space?
With dir, you do not preallocate the space.
With anything else, you preallocate, and can have fancy features like copy-on-write, which really saves space.