I don't have a Xbox yet , Series X is on pre order, but if it is anything like my PS4 pro, I will continue to game in movie mode.Apparently the ghosting shows up mostly when VRR is enabled. I can see you have the Xbox One X you have not tried using VRR with that?
Also regarding the blooming, is it bad with subtitles or is it fine?
There is a pretty huge hit to the PQ to run game mode, and I personally don't think the slightly faster input lag is worth it to me.
To answer your other question, the blooming on subtitles is pretty bad.
However the blacks on letterboxes are so black, you will wonder how they pulled it off on a LCD.