Really just a question about how this works. I'll pose some hypotheticals. And I don't know enough about how x-heights measurements are specified, so I'll do my best and just hope my hypotheticals make sense.
Say Type Designer A makes a typeface (let's call it SmallXTransitional (SmallXT)) with an x-height that is .7 of the point size. Type Designer B makes a very similar one (LargeXTransitional (LargeXT)) with an x-height of .8 the point size. Assume that SmallXT and LargeXT are quite similar, except for the x-height.
Years later, along comes a layout project (say, a 16-page booklet), and the client wants two different comps from two different typesetters. Typesetter X uses SmallXT at 16pt with a line-height of 20pt. Typesetter Y uses LargeXT at 14pt, again with a line-height of 20pt.
What will be the difference between the two? Am I wrong to suspect that the difference will only show up in the capitals? Or perhaps the ascenders/descenders? Will these two hypothetical settings be quite similar in character (all other things being equal), as I suspect?