clark/kal/superman is a fundamentally sad person who lights up like a christmas tree when he starts doing the superhero thing.
Easy to say single superman sad, but to start talking about it in the context of his marriage and his family life? when he's truly become a man who has everything? That’s when it starts getting really juicy. Thus it is wise to look back to rebirth era superman to see kid Jon and Clark's relationship through this new perspective and how that affects their relationship now. Imagine a father who loves you deeply but is fundamentally distant from you. and a son who he’s put so much personal weight on, THE person who will make him feel "not alone," but the guilt consumes him because all he’s let himself do is love, and to desire being loved feels selfish.
oh and exploring his relationship with Lois as the person he opens up to about this stuff and yet, even with said communication, his state never truly improves. how would Lois deal with that, how she confides in others, lost roommates who she's grown distant from but reconnects with, or maybe how she feels obligated to maybe let his worse-off tendencies slide because of her own sadness she has made him "deal" with.
While Jon starts trying to be a superhero to get his dad to notice him more, he wants to be like his dad because he subconsciously felt his dad’s deep desire for someone like him to relate to and shapes himself to fit that image…
Jon Kent is defined by a kind of co-dependency Avoidance, denial, and an inability to think in terms of his humanity and only as a tool or a part of a whole(family, romance, friendship). Jon knows he's avoidant, he doesn't like thinking about his trauma or talking about it, he will suffer through it alone. Even in his deepest, most lowest moment, he speaks of his own trauma in terms of his family. His autonomy and individuality have been slowly chipped away by the prospect of being Superman. Superman does not live for himself, he takes risks and sacrifices himself for the greater good.
So ClarkJon’s sex should be passionate
The parallels of them both being driven by loneliness, but in different ways is perfect. If Clark can find some solace in Jon, and Jon can find personhood in being with Clark, the first time they have that breakdown moment of giving into one another, it's going to be cathartic. Passionate. Nobody else gets it quite like them.