I don't really understand the question. Gay and straight are forms of sexual orientation. You can't see if a guy is gay, bi or straight unless they are in the act of having sex. IThis is why some people are so confused by what "straight acting" means.
In terms of Masculine/Feminine, people are characterized by how they behave along the following:
Someone who is masculine would be on the masculine side of all of these (whatever they mean to you). Typically, people make assumptions, judgments based on mannerisms and physical attributes which causes conflicts because you can have feminine mannerism but with a very physically male body (gym queens, for example).