This picture is from Bicycle Quarterly.
Check out the rider position on this fixed gear winter training bike from 1950, built by Rene Herse. Very often one sees this small amount of seat post showing on older bikes. Frame proportions led to this appearance even on the bikes of racers, if you look at period photographs.
Riding position is the most important thing. Standover clearance is only relevant when you're standing over. At stops on the road, or riding rough terrain on a mountain bike, clearance matters. A smaller frame also seems more controllable on rough terrain. But a rider cruising on the open road only cares about relative positions of saddle, pedals and handlebars.
Note how level everything is from the saddle to the tops of the bars. Even the drops parallel the tops.
Saddle is slightly nose up. Most of the bike pictures I sampled on the Bicycle Quarterly site reflect this. That's what keeps you on the rear part of the saddle. Drop the nose and you will slide there.
You see it on each of these as well. Top and bottom bikes are randonnee bikes intended for long events. The middle picture shows a 1957 Cinelli road racing bike. Things didn't look too different by the time I got seriously interested in 1975. In the early 1980s evolution really took off. Cycling had been in the forefront of industrial development from the last couple of decades of the 19th Century into the first ten or fifteen years of the 20th. Then interest in automobiles and aviation pulled the majority of technological innovation away. Cycling was left to artists and artisans. Sure, things evolved, but because speed and horsepower would always be limited, industrial interest waned. The bike was a toy in developed nations and a symbol of the backwardness of undeveloped ones. Cycle sport might draw enthusiastic crowds, and various bike booms might bring surges of interest in touring and fitness, but when the big horn blows on the 12-cylinder chariot of industrial power, get that bicycle the hell off the road.
At this point in history, all things in cycling exist. Some people find and restore gems from as far back as the boneshaker era of the 1880s, while present industry leaders tout the advantages of their carbon fiber marvels. Artist and artisan builders produce modern versions of the bikes of any era. It's incredibly cool.
Sadly, the many small component makers of the early and mid 20th Century have been run into the ground by huge, voracious corporate competitors, so you can't find as much funky componentry as you could even in the late 1970s, but perhaps that will change as well. Indexed and integrated shifting systems present the biggest roadblock to that. But you can find headsets, hubs and some brakes with which to express your individuality.
The Big Three component makers have even allowed some cranksets to mesh with their exclusive, proprietary spacing. Just be alert for chain problems, like riding on top of the chain teeth of the small ring or falling in between and wedging the rings apart. That can even occur on brand-name matchups because the spacing is so critical with skinny-skinny chains.