Tamaranean Lance and Kryptonian Shiro is so cool!! And YES to everything you wrote. And did Lance kiss Shiro to learn his language in this AU?
Thank you! Thank you! I am really excited to try and do something for it this weekend!
And yes, Lance totally learned how to speak Earthen languages by kissing Shiro. I imagine their first being very similarly to Starfire and Robin's/the Titans (save, well, Shiro being basically Superman). Where Lance was trying to escape captures and basically destroyed stuff to free himself/not understanding Earth ways. Lance is very standoffish towards Shiro. His hot and cold attitude throws Shiro, cause on second he is getting a warning shoot, then he's beong kissed, then his being shoved to the ground while bring growled at. Like he is a very confused and flustered puppy by everything.
Shiro pretty assumes Lance is a slave of some kind by his outfit and his untrusting behavior. But when it is confirmed, Shiro shows little mercy towards the other aliens trying to recapture Lance. And he's a complete gentleman offer Lance his cape (assume the outfit is not Lance's choice) to cover up from the cold and a place to stay while he figures stuff out. And just being the kindest farm raised bean in the universe.
After a while Lance wants to stay on Earth and live with Shiro. Because one Shiro is a superpowered powerhouse of a being, and two he is so nice and patient as he teaches Lance about Earth. (In exchange Lance tells Shiro about his people, culture, and planet) Shiro learns Lance is like the polar opposite of when they meet, and he is very energetic and out going (and can kick his ass cause yeah of course he is a warrior prince). He helps Lance become a hero, and sometimes they team up, sometimes they don't.
(I am basing this largely on Teen Titans, some of the new DC animated movies, and the small bits of comic book knowledge I know.)
And like I imagine Lance floats when he is happy (not that Lance hides it most of the time) but Shiro finds it adorable. As well as they both speak Kryptonian to each other, because Lance knows what Shiro knows. And all of Lance's fashion choices drive Shiro a little insane, but Lance needs that sun on his skin.