ZFS isn't picky about hardware at all. You can do all sorts of bad, silly, dumb, clever, etc., stuff.
Don't confuse ZFS with FreeBSD. FreeBSD really needs stuff like decent HBA and ethernet controllers in order to provide a good NAS experience.
I generally recommend heterogeneous pools (pools made up of devices not all from the same mfr) for various reasons. I'm not sure mixing 3.5 and 2.5 drives is a good idea, but it probably wouldn't kill you.