It always depends on how you feel. If you are ftm trans but still feel lesbian you can call yourself lesbian. If you feel straight you can call yourself straight. Yes, generally, a guy who mainly likes girls will probably call himself straight. But that doesn't mean you have to as well. Also, a trans guy probably has a different experience to a cis guy and depending on how much being trans is a part of their identity they might choose not to use the label straight.

There are also terms for liking just guys (androphile) or just girls (gynephile) independent of what gender you are. But many people don't even know about them.

Ok

Well, your sexuality depends on your gender, not your biological self. So an ftm who likes girls would be straight, and an mtf who likes girls would be lesbian, regardless of physical transitioning progress.

Ok