Yes, that's correct – knights are the backbone of the human army, alongside archers. Regarding griffins: based on the lore of other parts of the Heroes series, we can say that the griffin occupies an intermediate position between tiers 3 and 4. In Heroes 6, the griffin is the weakest in the elite units (conditionally tier 4), and in Heroes 7, it is the strongest among the main troops (conditionally tier 3). Placing monks above tier 4, in my opinion, is absurd, and I already have cavalry at tier 5, so tier 3 remains for the griffin – it fits the lore, and it will be adjusted with the highest characteristics for tier 3 and the lowest growth.
Regarding the Lords – generally yes, the archdemon will be stronger, but there won't be any in the castle; instead, there will be ifrits at tier 6.
This message has been edited due to the relevance of the information
I'll leave a couple of attachments here.