I think its a very difficult conversation. I prefer actual massage and HE. In those close conditions sometimes it gets very interactive. I generally state my limit while booking appointment. PrEP is a red flag for me. I am glad they are careful but it can stop only certain things not all. I will rather not go.
I knew a well known performer, has lot of videos performing unprotected but also gives excellent massage. Once he started going on different track leaning towards performance. I was shocked. I stopped at that point, paid and left. I think he thought it was rude. For my next appointment with him, He went completely therapeutic and was fully covered all time. I got the message and stopped booking him. I prefer that over constant doubt. Since that incident I am very clear (may be a bit overboard) about limits.