I don't think Capela will do well as a rookie. Too unskilled offensively and learning curve defensively to do well at PF + not big enough physically or experienced enough to play as undersized big to do well as a center.
Give him a couple of years though and I think he'll be a very good player further down the road. A Larry Sanders level talent.
Larry Sanders is all around just longer than him.
A small bit longer but those two are reasonably close.
Larry Sanders - 6 foot 11, 7-5 and 3/4 wingspan, 9-4 standing reach
Clint Capela - 6 foot 10 and a half, 7-4 wingspan, 9-2 and a half standing reach
I think Capela is plenty big enough to play the center position with that combination of height & length and elite athleticism. Needs to add some muscle over next few years (as Larry Sanders needed to when he first entered league) but that should be doable over time.
In terms of skill-set, I think Capela will likely have to play center anyway (instead of PF) due to his offensive limitations. The big key for him will be whether or not he can add a jump-shot to his game. Larry Sanders couldn't and ended up at center because of it. Serge Ibaka did and was able to stay at PF. So for now, due to offensive limitations, I think Capela projects more like a Larry Sanders type center than a Serge Ibaka type power forward.