Yes, Unaware Clafable is solid. I've topped the ladder at some point with it before I tried some dumb stuff and tilted. Magic Guard Clafable is pretty mediocre btw, there aren't many things that rely on residual damage to win the match so more often than not you're not really taking advantage of it. However, there are a butt-ton of set-up sweepers whose days are ruined by Unaware Clefable--the likes of Cloyster, Salamence & Mimikyu just straight up lose, whereas they would be able to brute force through the Magic Guard set. There are some merits to using Magic Guard, though: you beat stall, although stall teams are few and far between so take that as you will.
Alola-Muk is a problem no matter which set you're running, though, so you must pack a really solid answer to it or not bring Clefable at all.