Scholarii (cataphracts) and Athanati (immortals) were the last remains of the 10th century glorius armies.
Varangians were Rus (sweden vikings that settled in Novgorod and later Kiev and ruled OVER Slavs).
Later Danes,Norwegians and Swedish vikings joined the Guard side by side with Saxon Huscarls after the qonquest of England in 1066AD.
The Slavic mercenaries of the empire were mainly Serbian heavy infantry (spearmen) and later in 14th cent Serbian knights.
That is the most inaccurate statement ever.
Half of Medieval Roman armies (byzantine) were profesional (payed through land incomes) espesialy ALL horsemen.
Stratiotae (in other eras known also as Cavalarii),Acritae ,Pronoiarii (large land owners) were some of them.
Also ALL imperial units (that stationed in Constantinople) were profesional.
In real Medieval Romans (Byzantines) merged the armies of the Republican and Imperial Eras.
The provinces had both millitias-as citizen soldiers-and profesionals and the capital had 100% profesional troops.
If you do not mind to lear please read
this.
I the SS timeframe there were more profesional troops than millitias than those described there.