Bryan Exactly. Normally tights are worn above the waist line of a Chastity belt, so it makes sense to wear the belt over.
If you go under then the tights aren't going to fit right, which is probably OK, but they will do something stupid like roll down. In any case, since the tights can't be removed they would make bathroom visits fun. In the latter case you can roll them down a little so you have a chance of peeing but it would still be unpleasant.
Thigh highs would probably be your best bet and might be naturally underneath your bands anyway.
As to "benefit", aside from what has already been mentioned. Thigh bands change the way you walk, similar to heels, but the combination of belt and band is sexier (I think, not like I can stare at my own butt). You also need to wear a skirt, are forced to keep your legs together, and are constantly aware of your belt and bands so they force a set of behaviors that are classically feminine.
