tires/snow rating / not worry? / chains are solution?

M&S is a worthless rating. What you're looking for is the mountain snowflake rating for extreme snow. If it's important to you, then there are a few A/T tires that carry it, like the Goodyear Wrangler All Terrain Adventure, Duratrac, and BFG All Terrain. When your OE tires wear out, I recommend you get one of these tires if you need all terrains and would benefit from the extreme snow rating. A dedicated winter tire is better yet if you live in a place with a lot of snow.