I don't think there are any risks if you get them in the correct size. If they are too small they will be pretty uncomfortable. There maybe risks of blood supply/clotting, but only if you get them too small or have health issues. Also as with chest binding you should give tissue time to rest. I don't know how long you should rest, but you don't need them when your sleeping.
I have some champion ones that work, but I think they only really work for my thighs. I got them in the same size as my underwear, but they work better with briefs. I'm at the upper edge of my size range, so going down a size would be really uncomfortable.