I'm not STU. I run XSA for fun as my car (Golf.Sportwagen) will never be competitive in any class, except perhaps at the small club level.
That said, much of my modding has focused on having it both ways - a tolerable daily and a fairly aggressive suspension at ax.
In this regard, I've played around with spring rubbers in the front and bump springs (instead of bump stops) in the rear. Both can be quickly added (spring rubbers) or activated (bump springs with packers) at the event in about 10 minutes and then removed before heading home. This allows a huge bump in spring rate for ax which can be undone and brought back to stock rates.
I haven't attempted yet, but IMO given the rules, someone wanting to be competitive regionally or nationally needs to go beyond bolt on parts to gain an edge in the alignment area....for example, make your own camber plates and do what is legal to provide clearance to allow it.
That's a interesting concept to consider. I actually remember hearing of spring rubber back in the day. Worth a out-of-the box consideration for sure. Spring rubbers are permitted in STU. Interesting.
While coils do offer a lot of adjust-ability, most of that is used to set the car up once and then leave it alone. Adjustable ride height, camber plates, etc aren't really adjusted frequently. But having all of those be dynamic instead of static or locked in during setup lets you tune the handling of the car to your liking. For those reasons, a true coilover kit will always be superior.
That said, a solid shock / spring combo will be very reliable. And if you don't know how to setup coilovers or don't have someone to help guide you through different ride height settings, alignment settings, and damper adjustments, then all the adjust-ability won't mean much.
I had Ohlins on my E46 M3, which was also in STU at the time, and PSS9's on my S2000, etc. I guess with that I am familiar with adjustability for handling, albeit I was young and dumber back then, and didn't fully grasp them. With the DCC shock, I wont me doing any adjusting from damping/rebound aside from selecting the settings in the car.
I do adjust front camber and front toe at the event as well.
Tires also...having dedicated ax tires and street tires are more work each event but allows the car to have a more comfortable dd ride.afterwards
I do have a set of wheels dedicated to the tires I use, no issues there. Way worth the expense and the hassle to transport, store, swap, etc. I'll drive to the events with the race tires, unless it's out of state, or in another region. Then I'll either talk someone into putting them on their trailer, or cram them in the back of the car.
I don't think I'll ever get to the level of a national competitor. I don't have that luxury of time and money. But if I did, then I would probably ditch the daily driven mindset and go all out.