About RBM i think the mod would be ok if the game was around 1400+ when plate armour was functioning but we're in 1084.
In my eyes RBM looks broken especially cav is a joke as are archers in vanilla.
In Bannerlord some armors are slightly anachronistic. But technological decline was much less significant in the Byzantine Empire, thus they widely used composite armors (lamellar, scale, splint etc.) even in the XI century, when all Europe was relying on mail hauberks.
RBM creators are a little bit too pedantic when it comes to armor protection and weapon penetration values. If they see full body scale armor with double mail and lamellar vest, they cannot just make it's protection values equal to mail hauberks and call it a day. However they are working with what they see, if TW created such strong looking armors, RBM will give it adequately strong protection values.
In general, if you prefer more arcadey combat with short TTK and fast engagements, you should abstain from using RBM Combat Module. The AI module changes, however, are too good to miss, even if you like fast paced combat. Unless you prefer the vanilla zerg rush cluster**** melee combat.
Cavalry in RBM is very strong, so you will have to use heavy infantry, pikemen, terrain advantage and ranged troops, in order to stop it. Yup, just like in real life.
BTW, RBM is highly configurable - weapon damage, armor values and modifiers, troop skills and loadouts - can all be changed through the xml files.