Mike in NC
Doesn't matter whether its a standard toilet or an ADA, the ring should be the same. What does matter is the elevation of the flange to the floor. If it is at or below floor level (say, if you have added tile since the flange was set) you may consider the thicker ring. As for a standard ring or one with a "funnel", it's all in preference. Some folks like the funnel because they think it reduces the chance of leaks. I personally prefer the standard, have set countless toilets with them, and never had a problem.