As an Actor I must say that in the past has worked differently depending on the situation.
The film making rises with the desire and the burden to tell a story.
And the role of the actors is to deliver the emotion wanted by the director and the script writers on screen and sometimes I have found it more efficient to focus myself on the kiss to keep the tension and the moment on that to let the audience understand the passion and the grip that was keeping this couple together for some reasons. And in this situation you definitely feel everything because that is where your focus is in that very moment.
Other times instead I decided to focus on the feelings and movements in order to let them see what was going on in terms of ‘’situation’’.
A potential situation could be anything from a reconciliation, a cheat, a lack of money, desperation, and any place where the two are living a peculiar moment of the script necessary to introduce what’s next. And while filming this kind of scene you don’t feel the kiss but the feelings themselves.