NELEUSMen's 3 Pack Athletic Compression Under Base Layer Sport Tank Top

I use us small size for my tees. what size should i order? thanks!

I'm 235 and wear a XL what size should I get?

I'm 6' and 230lbs, with a 45.5 chest. What size should I get?

I would like to wear these shirts under my golf shirt while golfing. Are these shirts a “ribbed” fabric, or flat?