Oh, Hartman and Farley very much had one of the all time great writers rooms. I very much feel that is what Adam Sandler owes his entire career to (he is a shockingly good dramatic actor, but he never would have been given a chance without the comedy background)
Hartman I feel was incredibly good at taking complete nothingburgers of a script and adding mannerisms that could elevate them. And there are some stories of him doing particularly good improv on a few sets. Hader very much “came into his own” after SNL and a lot of his best work was when he IS a writer, but similar deal and he does have some amazing moments on the show.
Farley is the one who I would actually give the nod. Basically every story is about how he would figure out something in wardrobe or do a weird mannerism to elevate everyone around him. And he made some god awful scripts hilarious. He still benefited a LOT from a solid writer’s room but, of basically all of SNL, he is probably the only one that I feel was better when he actively ignored the script.