I haven't owned/ridden fixed. I've built up 5 single speed bikes from old steel frames and use a regular wheel with spacers on the freehub with a 1 cog placed between the spacers.

I've used some 80s road bikes that built up fine but weren't a ton of fun because they were limited to a 28mm tire and I just didn't use the bikes much.
I've used a modern steel cx/gravel frame with canti brakes that was fun for having a 50mm tire on and riding smooth flat twisty single track.
I currently have an early 70s Peugeot set up as a single speed with 32mm tires and use it 1 time per week to commute to an activity that's about 8mi round trip.

It's a lot of fun- the frame angles are pretty aggressive and the chainstays are 460mm. It's an odd geometry for sure.