"long as we are on the subject, how rare is a 20 ga 2e, with fluid steel barrels and a straight grip stock?"

You won't get that information from Brophy; but you can get most of those questions answered in Jim Stubbendieck's book L.C. Smith Production Records".
The records show a total of 370 No. 2E 20 gauge guns out from of 393 No. 2 guns produced. The pre-1913 records DO NOT ID barrel type but do ID barrel length as follows:
25" - 1
26" - 91
28" - 185
30" - 85
32" - 31
and two guns were shipped with an extra barrel

And as to Smith frame sizes I'm convinced there are size differences in the very early Hunter Arms Co "R" sized frames based on personal observation. R frame size, at least for 12-bore guns, does not appear to become consistent until about 1898; and to support my observations, I have early 1890's ads where Smith quality grades and new number grades were being promoted in the same ad
As to Syracuse era guns, Buck Hamlin tells me that he has ID'd 5 different frame sizes used for Smith guns manufactured in Syracuse.
A standard 12-bore
A heavy 12-bore frame used for heavy 12 bores and light 10-bores
A standard 10-bore frame
An standard eight bore frame used for heavy 10-bores and lighter 8-bores
A heavy eight-bore frame.

period LC Smith, NY catalogs don't list the 8-bore as available, but I've held a Syracuse era hammer and hammerless 8-bore in my hands.