Cant go wrong with any of those three. If you dont already have those three, you might want to throw 885 in the mix. Durability in my opinion would be better than those listed and looks about the same. It's also cheaper than 915.
IME 845 can be a little unpredictable with regard to durability. Sometimes it wears like iron and other times it doesn't last all that long at all.
If going with a Collinite paste, I too would lean towards 476S/885.
The Glanz is simply *different*. AFAIK (never used it) it's much more like a typical sealant. IIRC it doesn't bead all that much, if that matters to you, whereas the Collinites bead like crazy.
Yea the small amount of carnuba in the Glanz wax would wear off quickly thus loosing the depth of shine whereas the Collinite would last longer in that area.
I will prep with Meguiars #9 or 1Z Metallic Polish.
Those will give somewhat different looks IME. The 1Z MP is "cleaner" looking but won't hide any flaws to the extent that #9 will. The #9 will look "richer" on some paints.