Vikings are fine if you think of them as a repping the Scandinavian kingdoms.
They underwent roughly similar architectural periods as Germany.
It’d be nice if the Feudal Age buildings for the Central Europeans were a bit more Germanic Migration Period-ish, if the Teutons, Goths, and Vikings were to continue share it.
The Goths, however, would probably make way more sense sharing a set with the Byzantines, if they were to get an Eastern Mediterranean/Black Sea type architecture set.
Wherever the Huns should go, I wish that the Steppe civs had a flag attached to them where their Feudal arch set would be more Yurtish.
As you Age up the architecture would look more like whatever region they’re attached to with the exception of like Archery Ranges, Stables, and half the Houses which would stay as Yurts.