Looking at the positions he played with Sunderland its very mixed. 11 starts as ACM, 9 as AMR, 5 as RW, 3 as ST, 1 as MR and 10 subs. He has a grade above 7, which is pretty good, in every position but ST (6.8) and 6.34 as a sub. Which makes me believe he's not an impact player, he performs best when starting. Which is definitely an issue here and I dont think he'll be starting in the short term.
But anyway it seems he's a really complete player that can perform in multiple positions, I'm not sure if that's better or worse as I prefer specialists since "wildcards" tend to be some quite good in many positions but not great in any.
Stats:
https://www.whoscored.com/Players/386634/Show/Amad-Diallo