Aside from Sam still having his psychic powers, what else do you write that's different than the show?
so very very much so i will just jot down a few
spn monsters are super boring (just dudes in jeans) so i like portraying them as super creepy and crawly
sam's powers are inherited from his mother's side of the family
having some demon blood is what allows him to be a semi-capable witch
after jess and ruby, i don't really acknowledge sam having any romantic relationships
sam actually hates castiel and just tolerates him most of the time
sam feels more compassion for monsters than hunters
he has a wonderful niece @lilyspaintedred
sam and lucifer have a very spiritually close relationship, sam can sense when he is on earth and can feel his pain (so stabbing lucifer is essentially like stabbing sam but sam doesn't mind)
around s13, sam slowly starts relying on magical weapons more than guns and knives
sam never gets over his pathetic fear of clowns
my headcanon tag and my sam lore tag are probably better places to read up on this (also this lil post)