It would seem from the gemara in Sukkah (25) that the hava amina to “lechdu bisukkah” by choson and kallah, that intimacy or romance wouldn’t be asur in the sukkah, granted that there is privacy (like the maskana of that sugya). Is there any mareh makom that discusses any romance being an issue in the sukkah? (from negiya b’alma to tashmish). Just curious. Thank you.
As you mentioned, it would be permitted, as long as there aren’t any pesukim or tefilos on the walls or in the succah. Also the succah has to be private, without too much night penetrating it from outside.