People says Gaskier and Sterek got the same energy.
While I will grant you both got a Tall, Dark and Broody With a Tragic Past, Stiles and Jaskier are just not the same, beside talkative and seemingly weaker then their Hot Shot Counterpart.
Stiles is pessimistic, strategically intelligent, so sarcarstic it draw blood, practical to the bone, ruthless as hell, interested in saving only his few loved ones, wants to be a hero, guard his tender emotions very close to the chest because the slightest uncaring touch hurt like hell.
He is spunky, jumping into the fray to save the world with nothing more than a bat, a metaphor for his determination and bravery.
He knows he doesn't stand a chance. He is going anyways because it has to be done.
He is like a dog with a bone.
Jaskier is hopeful, socially intelligent, lyrical, full of love for Beauty and Romance, whimsical and unpractical, always wanting to save everyone, wants to witness a hero, shout out his emotions, fearless of getting hurt, end up hurt, heal, get back into the fray anyways.
He is feisty, setting out to love the whole wide world, including people getting into deadly battles, with nothing more than his heart, wide open.
He knows he doesn't stand a chance. He's there anyways because it's where it's happening.
Their personnalities, the ways they function, and what deeply motivate them (beside Good), is really just not the same.