There's no way the clashing headline options on the main two stages would be Wet Leg and Wunderhorse. Also the Sunday second act is literally co-headlining.
FO can get very busy, but to my knowledge never stopped people going in - they also have a big screen outside. What you do tend to get though is a massive barrier of trolleys just inside the tent - which imho should be restricted access. Especially as I expect Kneecap will be quite a lively gig!