After reading this entire thread, which was well written and thought out, I ordered my upfitter kit for my 2021 GMC 3500HD Denali DRW. My interior is deep Atmosphere, and I have the keyless start.
For those interested I ordered kit #84942074 from GMPartsDirect.com. It took exactly a week after I ordered it for them to ship it, but I just got word that it is on the way. This was by far the best price I had found in searching. It was $137.25 plus $18.76 in shipping or $156.01 in total.
I read where several were having issues in getting it delivered as a kit, instead having to pay more for each piece. Hopefully those issues are now resolved.
Good luck everybody on your installs.