For comparison...

Pike's Enterprise:

Daedalus:

I figure the semi-circular forward hull is a little over one deck thick, say 3
meters, allowing for hull plating and internal stuff. So the whole thing
would be about 80 meters, or around 190 feet.
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So about 3/4 of the length of the Enterprise's saucer section, then.

Still, this design would also look good in a larger scale, too.

But it's important to remember that the Constitution-type vessels were supposed to be the biggest and most advanced ships in the fleet during the TOS era. So any other ships from that time (or earlier) should be smaller and clunkier. The Franz Joseph designs are a bit of a cheat, I think, since they're just rearrangements of the existing Enterprise parts.

That was my original configuration. Then I decided it looked more
interesting with the "fin" down the back rather than the belly. Perhaps I
should reconsider.

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I think the "belly fin" orientation looks a bit better because we're so used to seeing the angle of the Enterprise's connecting dorsal, which the "belly" look echoes.

Since they mixed and matched footage with rugged, manly abandon, no
surprise there!

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Yeah, there's a lot of mix-and-match footage of the ship. My own personal take is that the ship "really" looked like the series production model throughout the series, despite the visual inconsistentcies (and the remastering crew has replaced all of the pilot shots with CG shots of the series version, too).

I hope to see JB's design all tricked out with windows and markings at some point. That would be neat! Kinda surprised that the nacelles don't have sensor spikes like those seen on the pilot versions of the Enterprise, though.