I believe that love is when you love a person soul. And sex is physical attraction, because sex can be practiced without love. But it is possible to note the fact, and many probably would agree that it is much better to have sex when experiencing feelings of love for this man. The sex becomes more imbued wonderful emotions. In his youth, many just have sex without thinking about love, and at an older age and we want love and sex. This is just my personal opinion about this issue. But clearly sex is fine in romantic feelings.
I think there is no difference in process but huge difference in what it means for you. I’d like to explain my opinion at example with food. Imagine you have the wolf in the stomach. And there is no difference what to eat for you. You just want to eat something to become not so starving. And try to imagine that you’re testing something very delicious. You are enjoying it. I’m sure you’d like to regale your girlfriend with it and become sure that she is enjoying it as well. The same is with sex. You just have sex to satisfy your instinct. But you share your emotions and care about your girlfriend while making love.