I think Jackill
had a few designs that numbered near the 100 mark or above, but those were mainly transport/tugs that served as support vessels. I think his Jenghiz class destroyer and a few other designs number between about 50-80, because the Jenghiz was an upgrade of the FJ destroyers. But many of the designs I've seen in various sources only have maybe 20-40 vessels max, and even then it tends more toward the lower end of that spectrum. When you consider how many designs a power like the Federation has if we include most of the regular non-canon sources (Jackill's, Ships of the Star Fleet, FJ's TM etc), then it doesn't make a whole lot of sense to build loads of every design. Only what you need per design.