Regarding the ships scales:
Although I like the bigger scale for the Constitution class (mainly because it enhances the size difference between her and the NX class so it looks more like they made progress), at around 400 metres I think everything would be oversized. The windows would (I think, because I only did rough measurements) be around 1 metre high and the wider ones around 2 metres wide.
Furthermore, wouldn't the shuttlebay be too big for the shuttlebay sets (TOS and the films) we've seen? And I think the bridge (on the TOS ship) had to be shifted back to align the knob on the back of the dome (which I presume is the turboshaft) to the bridge set.
And of course there are the docking ports which would be way too big (aren't they oversized already?).
So, I really would like them to be bigger, but I think they still work better at the lower scale (327 and 344 metres, option C). Also, the small size difference between Constitution and NX could be explained away. It could be that Starfleet wanted mainly faster ships but didn't have the technology to make the ships bigger in addition to that (limitations of the warp drive maybe). This could explain the huge nacelles on the Constitution class. It's built to be the fastest, not the biggest.
And for the Oberth, I would also rather take the 10 ft decks. There has to be some space (for structural members, conduits ...) between the decks.