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Do you sweat a lot when you sleep? Down's alright if you can dry it out - possibly ok in the US in summer...
Personally I've stuck with Primaloft for insulated clothing, it stays warm when it's wet and dries quickly - if you're on a budget/not sponsored, buying for long-term use and in UK conditions I really struggle to justify buying down stuff.
Rab vest weighs ~190g, Patagonia jacket ~270g with a hood. Both wash easily if needed. The pack size is larger than down for both, but the Primaloft Gold stuff in the vest especially is really warm. I've slept in both without a sleeping bag and used as an extra layer with a 2 season bag and been fine, I think I'm a pretty warm sleeper.
Down jacket (which you'll need for riding) and half sleeping bag. Or just wear leg warmers and down jacket and hat.
Yeah until you get out there and really try it, you won't know what you can deal with. Me? I can sleep totally rough with nothing and I'm happy enough. But I remember the first time I went away. Fuck I had so much stuff. Every time since I took less and less. You learn more about yourself and what you're happy with and what limits you can push. Last time I went touring, it was with a silk liner and rab bivi and inflatable matt. And even then I slept out without the bivi a lot when it was nice.