I would trade anyone in the right deal. I generally would prefer to trade from the upper minors than like Jersey Shore or FCL. For example I wouldn't move like Estanista as a throw in, but if he was the key piece to a good reliever, sure. It is all about getting the value for what you are trading.
For the Lee/O'Hoppe group - If the Reds loved O'Hoppe and would take him as the lead alongside another good player like Lee or Brown for Castillo, absolutely. Probably the same for Montas or Mahle.
I don't really know what I would trade McGarry for because the thing is probably not available. I guess a conversation about one of the Marlins starters or Tarik Skubal. They don't make me want to do it, but you have to a conversation about it. He is pretty untouchable and probably closer to Abel/Painter.
As for those two, I know you didn't ask, but it is the Red Sox are taking offers for Devers tier, or something like that.