I've added some engine details. I've also done a position test and I can see that compared to the model my engines appear to have a slightly larger diameter. So I will have to scale them down a smidge.
And the underbelly which has not yet been greebled.
A far as the sub-light engines are concerned they are some form of fusion engines. It seems to be the prevalent type of engine around that time in the book Star Trek: Spaceflight Chronology. I'm roughly basing my time line roughly on this book.
The warp engine is going to be a something related to fusion with anti-matter spiked deuterium for fuel. The fusion reactor would roughly be a primitive equivalent of the Warp reactor in later designs. This matches the Spaceflight Chronology book they have some their warp ships using this anti-matter spiked deuterium. I think this also ties in nicely with VOY: Friendship One. Because the Friendship One probe had antimatter for fuel. Yet, it doesn't make sense that earth would have the technology to make anti-matter that can be used at the same 1:1 ratio we see in 23rd century designs. Thus I would conclude that technology for making anti-matter was developed enough by 2035 to be used in small amounts for space craft.
Side note: As for the Phoenix I'm betting it didn't use anti-matter as WW3 would have made it in short supply. I'm also thinking that Cochrane used the nuclear warhead to make the reactor for the Phoenix.