The single Ohlins DFV adjustment dial affects both the compression and rebound. The rebound has a more pronounced effect than the compression. I was told 2:1, but that wasn’t in the manual so I’m not confident in that as a fact. My manual says “The adjuster affects the rebound, and also, the compression damping to a smaller degree.”Another option for the S550 is the Shelby Double Adjustable set. Uses Penske internals developed on a shaker rig the right way, and IIRC the strut housing is made by Cortex.
BTW, I believe the Ohlins DFV are single-adjustable, though the adjustment may affect more than just the high-speed rebound that Koni yellows change. The DFV are higher-end street shocks, the TTX are Ohlins' motorsports line.
If you look at web sites for Ohins, Bilstein, Koni, etc., you'll generally see their offerings broken down into "street" and "motorsports" lines. TL;DR: High-end street shocks are $1-3K per set and use off-the-shelf valving and adjustments to work with a variety of spring rates. Motorsports dampers are $1-5K+ per damper and are typically custom-valved for each car setup, with the adjustments used to match pairs and fine-tune handling - major spring changes mean revalving, and they get rebuilt regularly. If going the "motorsport" route, find the person you trust to do the tuning/revalving/rebuilding on your shocks first, then discuss brands with them.
Always remember that the more knobs you have to play with, the more ways you can royally foul things up.
I noticed on the Vorshlag site they mention 20 clicks of adjustment. Mine has 30 clicks. They come from the factory at 7 (1 being firmest). My second day out, I changed it to 10 for both front and rear. I’ve currently got mine at 10 in front, 15 in back. I’m sure I’ll keep mucking around with it.