Alaska's bag fee page is pretty clear, I think: two free bags for oneworld Sapphire up to 50 pounds each, three free bags for Emerald, with a $100 overweight fee per 51-100 pound bag regardless of status. Two free bags for First (and they don’t stack, so a Sapphire in first gets two bags up to 50 pounds).

(edited to correct Sapphire/Emerald mix-up)