Based on my limited experience with the demo of EOIV and EOU I'm aware that the order that party members and enemies take actions in combat is determined by some hidden value. Turn-Order has been mentioned by some skills, and I recall reading something in EOIV that spells reduce turn-order since they take time to cast. I'm looking for more details on what effects turn-order, along with how it actually works (i.e Do certain classes get a bonus to turn-order? Do certain weapons? et cetera).
What determines the turn-order in combat, and what can influences the turn-order?