Realistically, the red-brick set should be used for central European civs- Bohemians, Magyars and Poles. The old Cenrral European set (Teutons, Goths, Vikings and Huns, because… sigh) would be more accurately called “Northern European”
The original Forgotten Empires mod had a White-brick architecture for Slavs, (aka, Rus with Bulgarian-looking Boyars) while the Magyars used the Red-Brick ; that set should be brought back IMO, and used for the Orthodox civs (Slavs, Bulgarians, possibly Lithuanians? they can work either way tbh, since the Grand Duchy’s major cities were all Orthodox Ruthenian cities, but the noble elites ended up converting to Catholicism and so did the Baltic peasantry).
But since the devs haven’t really been looking into that, we now have 6 civs sharing the same red-brick set with Orthodox crosses.