Does Skyrim Elder Scrolls have a extended level perk so you can play Dawnguard without worrying about your max perk before Dawnguard and you will able to have all the perks you need

If you mean the Werewolf and Vampire perks, these are not earned the same way as regular ones. As a Werewolf, progress towards new perks is earned by eating the hearts of slain victims. As a vampire, progress is earned by killing enemies with your claws or life drain power. So even if you started Dawnguard as Lv81 with all perk points spent, you can still max out both the Vampire and Werewolf perks. Dawnguard adds no other perks, so a Lv81 won't miss anything out in that regard either.