According to 82games data, Tatum played on average 13 min/gm at PF and 21 min/gm at wing. Last season we played a lot with Theis and Thompson together, until we traded Theis. Even if he plays more at PF or more accurately, the team plays with 1 big, to me, it is still only going to be 16-18 min, leaving a lot of minutes for our PF by committee crew.
Grant Williams and Semi Ojeleye played about 17 min each last season, in the games they played (they both missed some games). I expect that in any given game, the main PF trio of Parker, Williams, Hernangomez (and maybe a little of Fernando mixed in) are going to play at least 24 min combined and maybe up to 32 min combined.
The coach can decide who plays based on match ups, who is hot, whatever. Or one of these may emerge and get the majority of the available minutes. Parker's career production is far better than Williams or Hernangomez but we shall see.
I am fine with the trade. Dunn would have been a nice defensive option off the bench but we need that less than what we should be able to get from Hernangomez. I didn't expect much from Dunn (and certainly not Edwards) and I don't expect much from Hernangomez.