They should both work. I've never tried using both at once; it's possible that one effect overwrites the other but that seems unlikely to me. I don't have access to my PC today, so I can't test myself, but I can say that vampirism is definitely irrelevant to the equation. Both the potions and the power should work regardless.
If you have any experience with the Creation Kit, you can look inside to see how both Fortify Archery and Berserker Rage work. I think they both apply a "Mod Physical Damage [multiplicative]" effect -- 2.00-times for Berserker Rage, and (1 + <mag>)-times for the potion (where <mag> is the potion's magnitude).
They should both work. I've never tried using both at once; it's possible that one effect overwrites the other but that seems unlikely to me. I don't have access to my PC today, so I can't test myself, but I can say that vampirism is definitely irrelevant to the equation. Both the potions and the power should work regardless.
If you have any experience with the Creation Kit, you can look inside to see how both Fortify Archery and Berserker Rage work. I think they both apply a "Mod Physical Damage [multiplicative]" effect -- 2.00-times for Berserker Rage, and (1 + <mag>)-times for the potion (where <mag> is the potion's magnitude).