I'm not particularly anal about keeping any of my bikes to original specs/equipment. I tend to think a bike is "acceptable" if you can ride it. The only one that's really close to original is the PX-10, which I'm currently in the slow process of refitting. The only non-original thing on that bike when I'm done should be the rims (bye, bye tubulars, though I have a spare normandy/mavic tubular set) and the shifters, which will be Simplex retrofrictions. I'll keep the original shifters, though not on the bike. Personally, I think a restoration would have period parts and not necessarily the original components. More modern parts, or out of date parts would be a rebuild.

A fixie is a fixed gear bike. One speed, when the wheels go round your legs go round and vice versa. No coasting, great for developing cadance. You might consider rebuilding one of your bikes as a fixed gear, the ride is subtly different and quite a bit of fun as well. Older bikes, because of their horizontal dropouts and lack of braze-ons, make particularly good fixed gear conversions.

I see a lot of mis-identified "px10"s-- generally, the px's had chromed rear stays and were made of Reynolds 531, although this is not true of some later PX models. If you need parts help or some idea what was on that bike, I can point you towards a couple of websites that contain generous info. You'll also run into some odd/old threading issues on the Peugeots.

The term "vintage" and "classic" have been batted around here a lot, and frankly, if you ask five different posters, you'll get five different answers. There's no sanctioning body, so if you like your bike, and it's older, go ahead and call it "classic" or "vintage." Your defintion is probabaly as good as anyone else's.