“Sous peine” define clearly a risk (a “peine” is like a sentence, a judgement), but a risk that you don’t want to take (EX: Restricted aera, do not entrance, “sous peine de” prison sentence).

“Quitte à” is different, it define a risk that you know but you want to take to have X (EX: I want really to finish this game “quitte à” be late at class).

Sorry but without examples I don’t know how to explain that