Good question and one we are likely to have an idea of very soon, starting with the Draft and off season.
One thing I would look at to understand what he believes works in the game of basketball, be it college of the NBA, is what did his Butler teams look like? He coached those teams. But before that he specifically constructed those teams in his vision. He took level B players (Hayward was a diamond in the rough...) and built a great "team". That's how they competed.
To me those teams had the following characteristics:
1. Requisite size and length across the board and by position
2. Defensive toughness, physicality and grit across the board as well - similar to the Baylor team this year
3. Ability to shoot threes - athleticism on the wings
4. Ability to put it on the floor a bit - at all five positions
From an article in the Athletic:
And as for what Brad Stevens is now stepping into, what are the biggest challenges he’s facing?
Vardon: Stevens spent quite a bit of time this season, what’s the right word here, complaining about the roster? He hated the idea of having to start Daniel Theis and Tristan Thompson together, there was no depth on the wings, the guards were too small and on and on. The challenge for Stevens is of course to address this and surround his two stars with the right mix to contend again. Can he use the assets Ainge sat on these last two seasons to acquire Bradley Beal? The Wizards don’t seem to think so, but that’s the challenge for Brad. It’s time to spend what Ainge compiled and make a run at the Finals. Soon.
We could add another wing this off season but frankly if we retain Tatum, Brown, Fournier, Nesmith and Langford I think we have enough there. I expect to see more physicality added across the board, but particularly at the 4/5 and 1 spots.