They all have tables for 2. The only exception that I can think of would be SciFi, since they are not really tables.
The ADR system has a pre-determined number of tables of 2-4-6 etc. per restaurant. I doubt the odds of getting an ADR would be any different for a group of 2-4-6. Larger groups would be harder. The chances of getting your ressie, I think, are more affected by where and when you want to dine.