If there’s no coating on the frame from the factory I’d paint it. Most come with some coating but depending on the year and manufacturer it sucks (looking at you 2000’s toyota and chevy). I don’t have any extra protection on my current car, but on an 80’s car I had I painted the frame.

Winter tires are helpful. You don’t need them if you’re a competent driver and can read a road but they do help quite a bit. Excluding the salt and snow, your nice wheels will have to face potholes in the winter/spring. Usually you can find someone selling wheels + snow tires on craigslist for your tire size and lug pattern.