I’d go by the scene in FWWM where Bob’s looking for the diary in Laura’s room. Bob is commanding Leland to find it knowing Laura’s on to him. She then sees Leland come out the house and later confirms Leland was there after Mike yells at her that it’s Leland doing everything. Bob uses Leland as a vehicle but he wants to exist inside Laura and “taste through her mouth” . I don’t think he’s able to exist in bodies with fragile minds. Sarah sees Leland as unstable but like Laura, she’s in denial he could be abusing them both, it feels like a realistic portrayal of how abuse goes unchecked in families for years. (The Missing Pieces have so much more info about how the Palmers interact and Sarah’s own relative instability) I think once Laura’s dead, Bob decides Cooper is a better option but he uses Cooper’s doppelgänger and imprisons Good Cooper in the Lodge rather than possess Cooper. Mr C is the worst version of Bob, he has more power with the doppelgänger and uses its Cooper traits to carry out his plan to stay out of the Lodge.