I used to have 2016 YukonXL SLT without magnetic ride on 18” wheels and had installed Michelin tires, and my friend had Denali XL on 20” and Michelin tires.
I drove my friends Denali and it was not much difference.
From threads about harsh ride, I know many downsized from 22” to 20”. And also I believe Michelin tires are little smoother. The 2015-2020 had harsher ride than 2014-older; and it looks like they made it better in 2021 and also added independent rear suspension, first time for GM large SUV.
I currently have 2021 Suburban RST without magnetic ride and on 22” and it rides pretty nice! (I originally was looking for 20” when upgrading from 2016 due to harsh ride complaints for 2015-2020, but with short supply I ended up getting RST on 22” and now I don’t think I want to downsize to 20” because it rides pretty good)