Rerun C0 Baizhu Alhaitham Quickbloom & C0 Wanderer Overvape | Spiral Abyss 4.6 | Genshin Impact 【原神】 

In my opinion, Alhaitham is still better with Xingqiu, Kuki and Nahida. I haven't tried Furina C2 and Nahida C2, but Nahida C2 should be better for Alhaitham.

Alhaitham, Nahida, Furina and Kuki. Very deadly, but also very suicidal

In theory alhaitham, nahida, kuki, furina is the best team (but is a bit suicidal, cause everyone except for alhaitham stay at 50 % of HP most of the time). The cost confy alhaitham team is the alhaitham, raiden, furina, Baizhu; is better than alhaitham, kuki, xingchiu/yelan, nahida; but worse than alhaitham, furina, kuki, nahida. Nahida C2 buff hyperbloom and spread aprox the same amount, so there is not big variation, and furina C2 increase the teams where use alhaitham + nahida the most.