I have an i3Rex, dont know much about the S version.
Snow Tires & Freeway Driving - Its a great city & highway cruiser, its the 2nd BMW I ever bought without ever driving it before getting the keys, I am not an EV person but a huge Bimmerhead, I am impressed how fun it is to drive. People with 19s can get snow tires, if using all seasons there is a traction mode adjustment in the iDrive the genius suggested.
Year-round driving up in the mountains - If you manage the modes and battery, I can get almost 250 miles to charge/tank. Worse case scenario you get 2 gal of gas. Unlocking the Rex menu is helpful because then you can run the Rex at 75% or below and not use up all the battery if you wanted.
Legroom - All depends on your size....
Overall comfort - Nothing compares to MC seats from 5+ series. I miss them in my 1 and will miss them on my next M2/3/4. M5 & X5 have them, wife complains about the i3 seats, but she got used to MC seats for 4+ years. Even my E34 sport seats are more comfortable than the various seats in todays 1/2/3/4 offerings. Problem with the i3 seats, is adjustments, you have forward & back, tilt back tilt, and the height adjust goes on an angle. I find it tough to get the perfect setting because of notch points of where it locks.