I am a bit concerned by the change in feeling/vibe the Tsi-Hu now give off. Part of what I liked about the first concept was that it made them look like a solidly grounded and somewhat intelligent enemy. Clothing, a lower build, a sense of mystery...
This one without the clothing and with its body being made to look far more aggressive in nature has kind of lost that sense of it being an intelligent individual, and feels more like a random/throwaway enemy you'd find dropped into any old game. You know, the mindless mobs that just run at you and you don't really care about. I think you might want to give them even just a partial cloak or something to add back a bit of that hidden, mysterious, unknown vibe. Clothing also hints towards intelligence, and with a slightly less threatening physical vibe gives the impression they might be more likely intelligent rather than something purely there for killing/fighting. Any little trinkets or additions that would imply they have culture is good I feel as long as it doesn't look out of place. The taller body with the crazy skinny midsection is I feel kind of overused, and makes this thing seem far more generic, and less real (a thin midsection IRL is a bit questionable, especially for a biped).
These heads also are far less identifiable and more... almost insect and alien in nature. While having it be a human copy isn't great, I did like how it was close enough in the first one to help it feel more associatable to humans and thus intelligent. New one has larger jaw/mouth area, higher eyes, more angly spiky bits and as a result negative space with the quills and stuff, but a smaller cranium further reinforcing the idea of lesser inteligance and being more of a simply agressive animal. Hordes of mindless enemies was more of the thought I had with the smaller kaijus, but making the Tsi-Hu themselves look less inteligent is I feel throwing away part of what helped them feel more unique and would have made them a more interesting enemy to fight in game.
These are just my thoughts on what I'm seeing, and I understand that it can be hard do to time and money limitations to outright go back and try over, but some quick additions like small scraps of fabric or another head design would be comparatively easy and may be worth looking into (and smaller scraps of fabric can be far more easily put into a model and animated simply as part of the normal skeleton system so it could still meet that goal of simplifying the process of making and implementing them). Fabric and clothing can also have patterns, colors, and other things on them that help them look more unique or vary their color in ways that make them more visually interesting than just having the entire creature be flesh and bony/metal like bits.