When you look at our TE situation, it is either two TEs this cycle or two the next. A second TE this cycle would be a good decision by staff if he's as good as Smythe. I believe that Welch's health situation [i.e. once hurt who knows later?] had the staff re-thinking one TE or two. I doubt that the re-think has anything to do with doubting Koyack or Niklas. They SHOULD be real good once they're out there all the time.
Regarding whether Kelly would go with a power offense. I believe that he is [amazingly] an "I can manufacture offense any way you want; just give me the right players" type of offensive mind. Kelly believes in cleverly designed systems. Therefore I believe that he will go both power-heavy PLUS receiver-in space mixtures as he continues to confuse people. Kelly's offense CAN power you even out of his basic spread and definitely when he finesses the second TE. The one thing that I doubt he'll ever do is use a fullback, other than a Niklas-sized TE or a third tackle in gimmick situations. Maybe someone knows if he ever played that way at Cincinnati.
Now here's a dataless speculation: I don't think that Kelly actually likes the combination of his spread ideas and Golson's lack of seeing quickly across the middle. This, if Everett is just too good to be bumped by Gunner, might PUSH Kelly towards a more run-heavy power offense. This is the way Beamer succeeded with Tyrod Taylor --- great tailback running and a QB who could hurt you many ways, but mainly NOT by quick deliveries. Everett will also have to develop the deep ball accuracy off play-action then. On the other hand, if Gunner somehow takes the keys, I believe that we will see the "old" Kelly quick-delivery offense with slashing runs through space. With Notre Dame's talent, there is no reason why such a team cannot blow you out at the goalline as well.