Williams is not playing so I assume he goes back down when Freddy is activated. Freddy is a switch hitter but has been better this year against LHP (though historically he does not have much of a platoon split).
I am guessing he plays against all LHP and some RHP. I would not be shocked if he is part of a CF platoon if Williams is off the roster. The only OF he has played was the tiny bit with the Phillies, but I am guessing they are more comfortable with him out there rather than Torreyes. So Torreyes remains the main alternative at 3B. Freddy in CF and probably SS.
The big question as you say is how well Didi plays. We kind of know that Didi will sit against LHP. I think he probably sits more than that though. Miller probably plays a bit less with Bohm playing more 1B (or even Didi against some RHP) and there is no reason to consider Miller at 2B or 3B any more.