Is the bigger rim/tyre size better for winter driving? What is the different between 15" vs 16" rim?

A narrow tire and rim is better for traction in snowy conditions. A wide tire has more of a tendency to "float" on the snow instead of cutting through the snow to get to the pavement. Best two wheel drive car ever made for getting around on snowy streets was the old Volkswagen Beetle. Car was shod with 5.60 x 15" tires and rims. Tall and narrow. With the engine behind the rear tires, traction was amazing. Of course you couldn't see where you were going due to no heat in the car to defrost the windows.

I have purchased three sets of winter tires over the years. Bridgestone Blizzaks purchased from The Tire Rack in South Bend, Indiana USA. Outstandinging traction during bad winter conditions. Tires have saved me from several accidents. I buy the tires mounted to rims.

That's my advise. Good Luck

the offset is the area from the returned of the rim to the face that bolts to the hub.this positions the wheel in or out with say an 8 inch rim a rear wheel force might have a 4 inch offset on an identical time as a front force might have a 6 inch offset a rear force wheel will stick way out and doubtless harm the fender or reason issues whilst turning the numbers you record are diameter and width of rim,no longer offset

Compared to driver actions, tire size matters little. Reducing speed and increasing following distance make so much more difference than vehicle or tire type. Your next biggest enemy is poor visibility. As long as you have good tread, size doesn't really matter.

PS; non-standard wheel diameter will make your speedometer inaccurate.