I changed my 20W50 mineral for 15W50 in my Ural when the weather started to get a lot colder but so far it's not been much less than -10: I expect it will get colder in Jan and Feb. At that point, I'll change it again for 10W40.
Synthetic would be more flexible and so would not require changing with a 10 degree change.
Personally, I still plan to use mineral as Urals need oil changes every 2000km or so and I don't think that the difference between mineral degradation and synth warrants a 200-300% price difference.
If anything I'll opt for semi.
If you go for 10W40 I've been warned to watch the oil for consumption. Russian rings are apparently as effective as onion rings in keeping oil in the sump, so a thinner oil could well seep through. My Ural does not appear to burn any oil between changes when on 20W50: time will tell with thinner oils!
I've recently bought these
used with handlebar muffs.
The battery si the oine that caem from the factory: a regular sealed battery.
I know that Hubert has two batteries on his bike! As for oil, I think he's used several different sorts but after a winter riding Siberia and the Alaskan (Dalton? Dawson?) Highway a few years back, I'm sure he could advise you!
Adventure: it's an experience, not a style!
(so ride what you like, but ride it somewhere new!)