A wax and sealant do the same thing. They just have different names as ones typically a synthetic whereas the other a more organic recipe. The sealant topped with wax is more for a visual reason in my mind. Typically a synthetic sealant will last longer than a nice glossy wax. So top one with the other and you get good durability and the initial look of the wax. Colli 476 is a paste sealant and solvent heavy meaning it performs better applied directly to clean paint. If not durability may be reduced. And it's not the most glossy of waxes. It's also incredibly durable so apply colli 476 as the base sealant and if you want then apply a nice glossy wax over the top but it's not really necessary.
As for having a pro detail a new car. They typically offer the protection from a nano coating meaning there is no need to use traditional wax and sealants as the coating will last approx 2 years or more. But also makes washing and keeping the car clean and looking fresh so so much easier. The initial cost of a detail on a new car is significantly less than on a used car and it's going to help maintain the new finish for longer.
With the correct maintenance the need for using clay can be greatly reduced. And to be honest you really need to expect to see some marring to the paint with even the most delicate of uses. A clay mitt can inflict terrible marring that almost looks like sanding flatting marks. But they are a lot quicker to use than traditional clay, but, not quite as at getting the finer contamination. With any clay or mitt, diluted QD or shampoo and water mix can be used. Even with bilt hamber wax I still will not use plain water. If you maintains your car, keep it well protected, use tar and iron removers when it's time to re wax and even when you do use clay you'll find very little bonded contaminants