The only wind noise from a Slimline II is that the wind deflector does push some wind down on the sun roof. I'm not going to lie, on the highway, I close the sunroof cover, that makes it completely go away. I will say I closed the sunroof cover on the highway before I had rack at all because I thought it was too loud.
For the mounting brackets, they are a two piece design, not one. They have a bracketing design the makes the brackets solid, but with it being a two piece, you can half rack it if you want. Which I will do when I have an off-road trailer.
For height, I've had both the older leg design and the newer design. Strength wise, I'm not worried with either. I went with the new taller design because I wanted the table. The table, while expansion, is awesome to have that, always easily available, never other items around it, never needing to strap it down, and can be packed at anytime, since it is under the rack, and obviously doesn't take up any space.
If you don't want a table, get the older bracket design, the modularity of a Slimline is just too good to pass up. Unless the rack is more for looks, and I don't mean that in a bad way, it's a legitimate reason for things, because other racks do look better, the Slimline is more of a workhorse than a show horse.