The biggest thing you can do if you get the 5.3 is the trans cooler bypass. The temp differences are 50 degrees roughly right out of the gate. Towing heavy loads its a crucial thing to maintain life. Some folks have ok luck with the 8 speed but I would avoid it if you can. The 10 speed like others said is hands down the better alternative for the 6.2... I have owned 6 or so of the 6 speed vehicles, not a single issue ever most of them were ran into the mid 100k area.
Suspension, yes the mag ride in the earlier years does not ride near as well as the refined later ones. If you want a nice ride quality, I recommend 20" wheels or smaller, non mag ride. If you want sportier feel, then mag ride rises to that occasion for sure. The AFM in any of these motors is a matter of when not a matter of IF... There are people getting 200k out of their lifters and others not getting hardly 10k. Turning off the AFM is key for longevity for sure.
All in all, across the platform each one is different and has their own feel, My 15 Burb is actually quite sporty in the corners after being lowered.
So drive it, get a good feel of what it feels like, then try to drive a few more in that same model year with different options to get a feel of what you want in one of these. The 6.2 with the 10 speed is quite a piece to drive where the motor and power band is always on demand in the few I drove. The 6 speed trans vs the 8 or 10 is the cheapest to rebuild in a longevity standpoint.