Im 5' 7" 275 what size would be best for me

2x I'm similar and it's a good fit for me. I had to get about 8 inches chopped off the bottom though, so the anti-snow sleeve inside was removed but I didn't need that anyway. I do think the bibs are much better than regular pants though for many reasons. I should have bought two of them.

Im 5'5" 175# whats my zize?

I purchased a L for my sons who are 6'2 - 155 and an XL for my husband who is 6'- 210. They used the bibs for skiing. If that is your intended use, the length may not matter so much because snow boots are forgiving. You're gonna want something with a little room to layer clothes underneath. My sons had plenty of room. I would probably go for the L.

Are these made to wear over jeans, or worn only as pants?

I wear jeans underneath of mine I just ordered them bigger

Are these ok to wear snowmobiling in NY?

I don't ride, i wore these in 25deg standing outside fo several hours, with a pair of sweatpants and stayed warm but I am also a cold climate person they also may not be as durable for riding, in my experience with friends pay the extra money for good riding gear.