For soft suspension Corolla is your choice.
Vitz is probably not as hard as Civic but it's not really soft. Vitz has good road grip so it's not too soft.
Cabin noisen stability at 100 cruising is good, not a lot, you don't feel you're going at 100.
It also has nowhere near the power of a civic or any 1.3-1.8 engine at initial acceleration.