Headcanon for the small Luke/Ethan community that I am a part of:
Luke is the doting/gushy one in the relationship. His PDA levels were bad enough when they were friends, and they just shot through the roof when Ethan finally tells Luke how he feels about him (bonus! Luke isn't even aware he's in love until Ethan tells him "Yo bro, I'm in love with you")
Basically:
Ethan: *breathes*
Luke: omg my bestie guys so great so amazing he's so cool and LoOk aT hIs aRmS
[After they start dating]
Ethan: *exists*
Luke: omg guys my boyfriend so cute so hot so lovely his mom literally took one of his eyes away to protect us from his beauty
Connor(or is it Travis?): he has nice arms
Luke: YES HIS ARMS–
Bonus-bonus! Luke has a thing for Ethan's arms cause THEY'RE SO NICE (he has a bigger thing for his thighs and he thinks he's being subtle about it but alas)