WP-RZ3O4 fuse holder

Hello, I recently purchased a WP-RZ3O4. When installing it I realized that it didn’t come with a fuse holder or the ring terminals. What size of fuse should be in the fuse holder when I pick one up?

Also, if I turn it off, does it stop drawing power? I am afraid of going out to a dead battery with it directly tied into the battery.