If I get a storage device, would it be possible I could load some apps on there, like YouTube, and would that work?
Also-would the hopper version work?
No, the built apps is all you get. It's not possible to add additional apps. You would need a hopper 2 or 3 with a hopper plus to add apps. But the simpler solution in your case with a wally would just be add a roku device.