I think of starship development as being somewhat analogous to the first decades of flight or automobiles when a lot of things are experimented with in seeking that optimal formula and configuration. We could see all kinds of different things.
I envision it somewhat different than "official" Trek lore that has had nacelles from the beginning. I see the ringship as being the clue where the first ships had (comparatively) massive warp coils housed in the rings. Successive designs might have led to smaller rings until someone had the idea to put a series of smaller rings with a cylinder (or two or three). Eventually you could see designs where the nacelles no longer had to be cylindrical as evidenced in designs like the TMP refit and the TOS Klingon battle cruiser.
Another consideration: over the years a lot has been said about the TOS Enterprise's
design, in particular the slim support pylons. as well as the massive saucer attached to the secondary hull by the narrow dorsal. In universe why would they design a ship this way? Perhaps design evolution led to a shape better suited to the kind of space warp propulsion they were dealing with and in tandem with advanced materials and construction methods that make such a configuration possible. The MJ design might look fragile, but it obviously isn't.
So I think it makes sense that earlier ships would have more likely been less exotic in design (progressively going backward) and configuration.
That leads me to the idea of a large spherical hull connected to a cylindrical aft hull by way of a skinny interconnecting neck or dorsal, and having nacelles supported by equalling skinny pylons. I don't see them having access to to the same advanced materials and construction methods as the TOS era particularly as the 22nd century is supposed to be "more primitive."
Of course my reason (out of universe) is that the design looks so dorky.