I’ve often thought it’s a great shame there are really no obvious “tells” regarding who will be compatible in bed. I’ve had a reasonable amount of sexual experience over the last 45 years (when you start at 15 and spend your teen and early adult years in Europe, that’s not difficult) but I’ve never come close to being able to determine in advance whether or not sexual compatibility is present.
As you rightly say, best to find out as soon as possible. Good luck with your search.