I’m being told all gas class A are on the same chassis ??

My coach is 31' built on an 18K lbs chassis with a 190" wheel base and it handles very well. A light grip of the steering wheel is all that is needed. Handling, control and ride comfort is going to be a very subjective determination. What is perfectly fine for me might be a down check and walk away from a rig for you. If you're looking to buy and have concerns about road performance then test drive as many different configurations as possible and make your own determination.

Were the people telling you the Vista does not handle well driving a 40+ foot diesel pusher?