The .270 is fine. It is beautiful country up that way. Keep in mind that it can get quite cold up that way by mid-September. Down is OK as long as you can keep it dry. If you like down and want to go that route take a look at Taiga. They are made in Canada and have some really top notch stuff:
https://www.taigaworks.ca/Sleeping-Bags-c7

Those prices are in Canadian $ so don't get sticker shock when you look at the page!

There are lots of great fishing streams in that area too.