score:8
That's the kind of gear I'd use when going to hike well into subzero temperatures. Attempting to hike in such a gear at +20Β°C, especially in humid air, you'll not be comfortable at all. It's a total overkill. Especially the pants.
What I'd use for such a hike:
For sleeping at temperatures -5Β°C what you really need is not huge amount of clothes, but decent sleeping bag. With filling made either of goose down, or even better synthetic. You can find sleeping bags rated to as low as -30Β°C.
As far as I know, in Cuzco you shouldn't expect torrential rains at that time of a year (or much any rain at all). So rain poncho doesn't seem necessary. Doesn't weight much though, so you might take it just in case. Preferably the kind that also covers your backpack. Especially if your backpack is not waterproof.