Can I disable DHs?

Yes, you can.
You can disable the DH before or during a game.
Before the game, you can remove the DH by putting the starting pitcher in the batting order in [Batting Lineup Settings].
If you put the DH in the batting order, you can choose whether to apply the Ohtani Rule.
During the game, you can remove the DH by putting the pitcher currently on the mound in the batting order in [Change Defense].