For starters. Based on the lore, the improved Kappas were poisonous. This would suit the Mazetours. The appearance matches this. Then, you can reduce the damage and health.
The descriptions of buildings and heroes should be changed, as they do not match the names of the creatures. And the translation of the mod itself is still poor.
Regarding the poison of the Kappas. In general, I mainly play Multiplayer and I'm not very knowledgeable about the lore, I'm more into mythology, so there may be many inconsistencies. There was an option to make the Kappas poisonous, but there would be too many similar units (lizards, Te). In the game, there are essentially 3 types of poisons - acidic blood, assassin poison, and an enhanced version like the Wyvern. With some effort, you can add the weakening strike of the Zombie here as well (which I did). That is, there isn't much room for creativity, so here, the choice was made in favor of diversity.
Added 16 minutes later
Well, the balance in RTF is probably the weakest point. I think that the creatures from NCF will take less of your time. I wanted to ask you: do you have plans to make a video review on YouTube?
Balance is very often a weak point in mods, unfortunately :/ RTF is at least moving in this direction and doesn't leave new races unfinished, which is a good thing. Balance of NCF - do you mean the mega-pack? That is, balancing them as neutrals? I myself don't use many creatures from NCF, because sometimes such units spawn on a mine - and that's the end of it :D
Video review - Oh, that thought has crossed my mind too. Especially since I'm doing a complete rework of Disciples 2 with additional branches, playable Orcs, Blackjack, stat changes, and more, it's time to create a group or something like that. I need to order a good microphone for this, because the one on my laptop/webcam is terrible. I've never done anything like this before. The question is about the format. It seems that the reviewers here are - Heroes for fan