Is there a difference?

Romance and sex and you feel deep feelings for someone your going out with that aren't the same feelings you have for your good girl friend you could love them both but it be in different ways you know?

To me the only real difference is the romance and sex.

Well a girlfriend should be someone you "spend lots of time with" and tell things too, hang out with, etc. So in that sense, without the romance, they're very similar.
With a lot of people, they see THEIR companion as their best friend.
But with a girlfriend, you might feel more open to telling more "inner" things, talk about things you wouldn't talk about with other friends, etc.

Even if it was the closest female friend you have, you wouldn't have the caring feelings about her as much as your girlfriend(its a totally different feelings), you wouldn't call your female friend everyday tell her your thinking about her, want to hug her, want to hold her hands, be around with her.

You feel warm when you with your girlfriend, you and your girlfriend's emotion will join into one, you know what's on the other person's mind without she saying it out.
You feel happy when your with a female friend(Not the warmth way you get from a girlfriend), you can laugh about things, joke about things.

Friendship love and Love relationship is totally different thing, it's like saying what's different between family love and friend love. And you do get FWB so yea you can have sex with a friend without being boyfriend/girlfriend.