Mop-up operations are the only thing that require your attention as some fights have mechanics, mostly just the 5th and 10th stage on the hardest difficulty. The current mop up's 5th stage is probably the most annoyingly long battle I've encountered in this game since launch, not in a fun or difficult manner either, just annoying. I would say it takes me 3~5+ minutes to clear that one stage alone, the other 9 take like 10~15 seconds each.
Most past events could be done just letting your party do whatever with a very few exceptions that might require some strategic set up. All available story content you can probably clear with 1 or 2 UR units...
I'm not sure about unreleased/future content.