Apart the shared claims on Roman Empires naming, they have nothing in common…
I mean, Ottomans or Russians called themself Roman Empire too, in their claims. It don’t mean they are the same.
The hype for Byzantines is simple, it’s probably the most important political entity of medieval age events, in europe. The crusades started because they called for help.
They have the first wonder of this age hagia sofia, which was built in the fourth century and rebuilt in the sixth.
The most impressive defensive structure in europe in this time, a gigantic chain which protected the harbours.
A really different architecture comparatively other europeans, really different equipments from them (heavy cavalry being cataphracts like in the east, and using mace tactics instead of spears).
A lot of unique siege engines, and crazy fire engines. Firethrowers units, fire grenades, fireships…
some of their Elites Guards were noble vikings, like Harald Hardrada which make money with byzantine guards, to come back in his land to become king.
They influenced the warfare of islamic empires, army structure and equipment of Ummayad empire were based on byzantine army.
Even in decline, they were the dominating crossroads of trade routes.
And just in term of pattern, colors ,clothings, … they would feel really different
They feels more assymetric in term of trope than HRE / English / Franks …
Vikings would be not crazily different from Rus’, or Andalus from Abbasids…
Abbasids are wrongly despised in the game, the camel focus is based on their berber mercenaries… in a caricatural way, sadly. And the science focus / house of wisdom is what we could expect from al-andalus and cordoba.
Vikings were crazily good to adopt the culture and religion of others… In feudal ages they would already shift from age of vikings to christiandom. And we would get the same stuff about being good at building wood stuffs. And Rus’ Lodya are longship …
Yes byz are original.
Holy Roman Empire = Germans civilization dominating smaller states like Bohemians, or baltic Prussans.
Famous imagery : Teutonic Knights, Landsknecht, Romanesque and Gothic Architecture.
Eastern Roman Empire = Remains of Romans Empire in hellenized lands, with a lot of middle eastern influence (in food for exemple). With cataphract, orthodox - roman / byzantine / greek architecture, firethrowers, hippodromos, and diverse poeple in their roman empire (some considering themself as Romans ) : Romans, Greeks, Latins, Venetians, Armenians, Georgians,… Versatile with inherited romans tactics for infantry, good navy and siege engine, flexible heavy cavalry, diverse mercenaries (armenian cataphract, petcheneg mounted archers, scandinavians / saxony varangianss, etc) … late / no gunpowder focus