Looks like it's from 1982ish per the graphics and the headbadge...which means it will most likely have French threading. The Vitus tubing kinda hints at that too.
I think you did pretty good with the buy, especially if it cleans up nicely, and you do not find any corrosion or damage on the frame.
The Stronglight 104bis "Drillium" style crank is a very nice bonus on this bike, same with the NR Campy RD. A Simplex SX610, which might have come with the bike originally would have shifted much better, but the slower shifting NR can be excused, because of ti's nicer aesthetics, so I would not bother changing it. The Vitus181 tubing harkens back to maybe a generation earlier Peugeots. It might be heavier than Vitus 888, 971, 980 tubing, but at least it's most likely CrMo (not really sure if Hi-Ten tubing was ever butted) and butted, per the tubing decal.
As you already noted, it rides good, which is no surprise for most C&V Peugeots, almost regardless of model and year.