The text for this will be huge, because it is massively important before people start to message me with comments and/or complaints about the loyalties of someone else's character app.
There is only one instance in which loyalty will be limited. If someone is a Sin or a Virtue, then they cannot be of opposite loyalty! Example: An Archangel with loyalty to Heaven CANNOT be one of the Seven Deadly Sins. This same archangel (let's call him Jack to make things easier) can be one of the Seven Deadly Sins if his loyalty is Neutral or Hell. (and even then, he would be unable to be one of The Seven Deadly Sins unless he Fell and became a Nephilim.) The same goes to demons and angels and nephilim.