The difference is in construction, adjustability, bushing stiffness, philosophy of the part being used as well as personal preference.
It's easy to say use the part that the race car uses but those are tuned in conjuction with a bunch of other parts and resources that the average owner will...
SInce you plan to track it, have you looked into rigid collars? Not many people consider them but they definitely help maintain your alignment under load.
Let me answer these, Yes you can show up at anytime, it's done on a first come, first serve basis, so whomever showed up first gets their car done first. Best to show up early because each car takes approxiamtely 15-20 minutes to do. Yes you can bring guests
Check out Momo wheels perticularly the heritage 6 or 2Forge. They're both based in Europe.
Momo: https://momomotorsport.com/shop/heritage-6?srsltid=AfmBOorFe1VjVawlgcnRhPEzyBL2NYzo-8YU85A4cszhsr5C0N6bet9r
2Forge: https://www.2forgewheels.com/wheels
I think the Subwoofer plugs can be purchased from here. The other plugs don't match up to what's been posted but they can probably swapped over for not much extra work.
https://mobilemaxcaraudio.com/product-category/speakers/speaker-accessories/
Looks like you chose the perfect time to become n Airtec dealer, they just launched their own catch cans and undertray cooling plate. Ive been looking into catch cans since my car has an upgraded turbo.