You're on it...asking really good questions and getting great help from others here.
I appreciate your pause to focus on a rain layer...good thinking...and easy for all of us to over-think! Regardless of our zipcodes, wx is always the wildcard when we hunt...but especially up here because of the extremes and the remoteness.
On my moose drop-hunts when I'm living in a tent in the middle of nowhere for two-weeks, rain gear is my most important clothing item, and it is an excellent wind layer, so I'm reaching for it on a cold and breezy day as well. Bottom line for all of us on a sustained, remote Alaska hunt...we want to be absolutely sure that our rain layer does the job and will keep us dry when we need it...period, no doubts...especially of it's day after day of sustained wet wx...which Alaska can do to us. We sometimes hit the wx jack-pot, and experience clear and cold days with very little or no rain...it does happen up here...just don't count on it!
My moose hunt rain layer for years was HH Impertech (bibs and jacket). They were a good price performer, did the job keeping the rain out, and they were great as long as I wasn't doing a lot of physical exertion, which tended to build-up moisture from the inside. That said, I'd still recommend them on a moose hunt for someone coming from an environment where they will likely not need a rain layer in the future after this hunt. My personal moose hunt choice for the past half-dozen years has been (and still is) KUIU Yukon jacket and pants...they are the best I've every had for moose camp.
Sorry to be long-winded...really. You are going to have a great adventure for sure! BTW, If you find yourself on day two, three or four of blowing rain, and you start thinking that Mother Nature wasn't kind on your hunt, just keep telling yourself that when this sh-t wx breaks, the animals are going to pop-out and start moving...it's really true and they do. They've got to move after being hunkered down in the combined wind and rain...and when that happens you'll thank Mother Nature for your harvest opportunity that the crappy wx created!