Will having larger tires 20" will improve ride quality versus 17"?
Only if the 20" wheels are lighter than the 17" wheels, which is IMPOSSIBLE.
Is there a tire that will improve ride quality on 17"? Right now ride is good on smooth road but hitting imperfection causes vibration shakes.
Is this how ppv ride is or I can improve it?
What is your present tire size? GM OE for PPV is 265/60R17.
You want 265/70R17, if not taller.
Also, you likely need new shock absorbers.
PPVs are for catching speeding vehicles, they are not couches with wheels.
Un-PPV your suspension with stuff from squishier Tahoes, maybe that will make you happy.