Having worked as a professional detailer (REAL detailing, not a fancied-up car wash; a Bentley Continental, for example, would take a solid 18hrs of labor for a full detail) for a few years when I was younger, I have used a (possibly literal) ton of products, from the stuff you can get at the supermarket to special-order-only $200/8oz 100% carnauba waxes.
I am extremely anal about my own cars, especially my 328, and there hasn't been a swirl or scratch in its paint for years...
That said, Meguiar's NXT 2.0 is hands-down the best "wax" you can get without having to order online. I say "wax" because it has properties that are closer to a sealant, but it does give both the depth of a good wax and the gloss/shine of a good sealant, and it lasts a long time: visually, once-a-month is all you'll need; for weather protection, my 740i has still beaded after 6 months without reapplying it.
If you're going to use it, get a semi-decent random orbital buffer, a couple bags of pads, and some good microfiber clothes.
1) Wash car (two buckets; one for soapy water, one for rinse)
1.5) Wash wheels (do it so when you rinse the car off, you're going top-to-bottom so wheel cleaner doesn't touch paint)
2) Clay bar the car (the ENTIRE car if it has never been done)
2.5) Clay bar wheels (if necessary)
3) Wash car (get rid of the clay and quick detailing spray)
4) Polish (go from large to fine grit polishes; the more swirls/scratches, the heavier the compound you should begin with)
5) Apply Sealant (Griot's has some good, affordable stuff)
6) Apply Gloss (Meguiar's #21 "Hi-Tech Gloss", I think it's 21, is very good for auto-parts store stuff!)
7) Apply Wax (again, Meguiar's NXT2.0 is fantastic; DO NOT USE ANYTHING LABELED "CLEANER WAX"; it will strip off all the lower layers)
7.5) WheelWax is very good for keeping brake-dust at bay!
8) Clean windows/trim/etc
That's a pretty basic overview of how to get your car looking better-than-new. I tend to do a "quick" detail (4hrs) about every weekend in the summer, and a FULL detail every 4-6wks depending on miles/weather/etc. In the summer is when I use the nicer, more expensive, glossier waxes; when I do a "pre-winter detail", I use a strong sealant, apply two layers, then use Meguiar's NXT2.0 as it's the only thing that I have found to really last all winter, while giving additional protection above the sealant.
In my opinion, of course...
You might be a little misinformed. NXT is essentially consumer level #21. And NXT has cleaners (and fillers) to some extent which might strip some of whatever you're putting it over.