jimtx, good questions. We don't yet know if the MCAS was required for certification of the Max or if it was accepted as an "add-on" due changes in engine size, weight & pylon mount, and as you ask, what the MEL limitations are, if any.
AW&ST highlights an article today entitled, "Lion Air Probe Expands to 737 MAX Design, Pilot Training" by (Sean Broderick and Guy Norris), states in part:
I perused a 737 Max MEL found on the internet and the MCAS is not even mentioned. The STS is. You need one STS out of two. If you got an EICAS message about your MCAS it would be a no go. I would suspect that the MCAS was required for certification. Boeing certainly bypassed the opposite elevator input to cut out the MCAS. Did they bypass the cutout switches also. If so that would explain that crew finally getting to the cutout switches when their only hope was to keep electric trim against the MCAS especially since they let the bird get fast. OR should the FAA/Boeing AD also caution pilots that they will lose a system that they didn't know they had and be careful when loading up the airplane. I don't like the look of this for Boeing.