I found that Stamina around 7 is the most convenient, 6 or 8 is ok, lower it has an impact on player performances during the game. 9 or 10 they perform better in game but managing minutes for training and Game Shape is troublesome.
You have 4 stronger players, but players 6 and 7 coul also be usefull.That is, the difference is not so great with the starters, and they may be more efficient than a tired starter that spent 40+ minutes on court.
You can try "Coach pick from depth chart" and the coach will make the subtsitutions when he think the starter is getting less efficient than the sub.
You can also try "Let's coach decide", if you don't care about minutes played at a specific position (for training).
The coach will make the best use of your players, taking fatigue into account, but he might field some players at different positions than what you expect.