High downhill speeds could happen back when. Limited by rough roads. Limited by tires. On a fixed gear it is possible, at least when young, to pedal at 200rpm. At that speed counter-pedaling doesn't happen, or at least I never did it, but you can counter-pedal at 150rpm. Using a fixed to control speed is heavy work. Very hard to sustain on anything longer than a hill. But not impossible.
I did query both Othon Ochsner, Sr and Jimmy Walthour about scorching (riding downhill with feet up). Othon said Swiss riders had too much sense for that. Jimmy said it was a bit before his time but he had heard old stories. Said it was a good way to get hurt. There is no way to find the pedals again if you take your feet off. Only possibility is to wait until the bike slows down.
Part of the genius of coaster hubs is they require no more bearings than a plain hub. Also they use large bearings rather than the little ones in a freewheel. Bearings were still quite expensive and relatively rough when the coaster came along.
The 'path' in path racer is Brit for track. It just means a track bike. Track races happened on running tracks and on grass so a path racer could look much like a road bike.
The only switchable fixed/free hub I ever heard of was the BSA Duomatic. Which was also a twospeed. Not sure when that was introduced. Pretty simple inside so an early hub could have happened, don't know that it did.