Those are stupendously big tyres, with stock or with any other 4 inch tyre it’s got tons of clearance so definitely not a turnoff in general.
I’ll do some messy rides with the bud and see how much mud it picks up and see how it looks. (there is tons of room in the fork) If they hoover up mud like some tyres do, it’s going to be pretty chafey. If they clear fast I reckon it’s fine. There’s more clearance than with my 26 inch thinbike.
I am btw just assuming that both tyres are the same size, maybe Lou has less tread height, I have no clue. OTOH, I don’t know if I even want that much tyre on the back. I certainly don’t want to spend £70 on a tyre for a while!
I gather you can fit a Lou into a Fatty but it’s pretty tight. Don’t know about the Voodoo. (I saw a comment that the Voodoo’s not due back in stock til February now btw)