First off, why are you even considering Cancun except as a convenient airport? It's like Vegas or Orlando. There's no there there. Actually there probably is in the Mexican part. But I'd avoid the tourist part, it's 99 flavors of concrete glitz. I saw it from the plane. That was close enough.
Playa, obviously, I've said plenty about. I've heard good things about some of the other spots near there, less touristy perhaps, like Isla Mujeres. Also, though, probably less food activity generally. Although there was an article in Food & Wine maybe, about 6 months ago, about a new casually upscale restaurant in the Tulum area. Sounded pretty cool.
I would like to go to Merida. I know Dickson went long ago. By all reports it's the "real" town in the region, the one that preexisted the tourist boom, so I think the answers to a lot of your other questions would be there, though I can't say I have them....
One thing I would say is, even in the touristy areas-- except Cancun where real estate prices surely preclude it-- it's no great trick to follow your instincts to something substantially better and more real than the place that the busload of tourists behind you is being herded toward. The place we found in Tulum, for instance, just another 50 yards off the beaten path, yet a very nice family run place, not a tourist trap at all.