Maybe I can answer a bit and hopefully others can chime in...
1) The vents, haven't paid much attention to them, but from experience in other vehicles there's not much pressure going to these vents. Seems like the last bit of air from the system will come through these as they are at the end of the line. (May even be controlled by the floor setting)
2) Calling it a "rough" ride may be more of an opinion. It's a truck, not a caddy and coming from a German VW, it probably does seem a little more rough. The sound is probably coming from the beefy threaded tires. Still, can't say without actually hearing but more than likely if the truck is still fairly new and in good condition.
3) The TRX/Outdoorsman models have a heavier/stiffer suspension opposed to other 1500 models. HD rear shocks for sure. Some sit ~1" higher than sub models and some don't. These differences could make for a rougher ride.
4) I haven't leveled my Outdoorman yet, but I haven't heard of any issues doing so as many people have. I plan to for sure. If anything, depending on how you plan to level, you may need to change the struts and shocks...maybe someone else with personal insight can finish this off.