No, on the contrary, it makes it easier. Most girls like guys with at least a little muscle on them. They do NOT like guys that look like they are juiced up on anabolic steroids. If you are toned and with a little bit of bulk, but not overboard, it should help with your posture, which is important in attracting women. It isn't the only thing that you need to focus on, but it certainly helps.
no, its all mental. your physique comes into the picture but not as much as you think it does.
I think guys rely on that for a way to get girls to walk up to them. That's false - girls likely are not going to come walk up to you. They are attracted to vibrant, interesting, friendly, outgoing and confident people. No one walks to hang around someone sulking in the corner.