Our first motorhome was on a P-32 chassis. I did most all of the same mods you mentioned to make it handle better and it made lousy handling better. However, my name for it was a bread truck with a toilet and color TV! It basically drove like a bread truck.
My next coach was a DP on a 36' Freightliner chassis with solid front axle. It had a 55 degree wheel cut and turned pretty tight. I added FSD's, Henderson MCU's, Safe T Steer and a new bell crank. It drove and rode nicely except in really strong cross winds then it was a bit more to handle.
My Allure has IFS and handles really nicely but it is 42' and has a tag axle. The IFS seems to take rough roads better but when they are really rough, you still know it. I don't know the specific wheel cut on it but it turns really tight.... can almost get it turned around in the same space as the 36' coach.
We bought the Allure for it's apparent build quality and the PO had taken really good care of it (and I wanted a tag and DW wanted more slides, etc.). I don't think I would have rejected it if it had a solid steer axle.