twist- Noting that opinions are like...uhm...well, everybody has one

I'll toss out my $0.02. Note also that I use Collinite and KSG (but not on the same vehicle).
Since the Yukon is pretty big, and white is pretty forgiving, I think I'd go with easy-to-use and durable, emphasis one the former. *I* would rather use 476S than KSG (and I find KSG very easy to use) so I'd stick with what you're doing now. I kinda like the beading characteristics of 476S better too, it's a little more "self-cleaning" in the rain than KSG (at least for me).
For the polish, I'd use something from 1Z (probably their Paint Polish) and then put the Collinite over top of it. I did that on my Blazer and it turned out nice (and it's plenty durable). 1Z is about as easy to use as products get and their polishes leave a wax behind so you could even apply the Collinite after the next wash if you're tuckered out after washing, claying, and polishing such a big vehicle.
Again, that's just how I'd do it, but there are no other combos I'd even consider for this job (and I can think of lots of them).
Oh, and FWIW, I found that the plastic trim on my Blazer, which is quite possibly the same stuff as on your Yukon, didn't stain when I got 1Z Paint Polish on it. The PP even cleaned it up a bit. That sort of little thing can mean a lot (no need to tape stuff off). I put Collinite's 845 on it after using the PP as I was just a little concerned that the 476S might cause white staining; it usually *doesn't* but I wanted to play it safe. After I had two applications of 845 on said trim, I did put a few *very light, thin* applications of 476S on the smoother black plastic trim (not the really pebble-grained stuff) using a semi- W-O-W-O method and it didn't stain.