In France, it depends a lot on the lines : Paris-Lyon has average of 270 km/h (167 mph); Paris-Bordeaux clock at around 300 km/h (186 mph) while Paris-Brest is more at 200 (124 mph). It is interesting to note that it often seems ti correlate to the age of the line, with Paris-Bordeaux being the most recent.

Yes, but they are limited by the technology used to build the line, and by how the lines were traced, but not because their high-speed trains need to stop at every city center or run on "winding" tracks, as is the case in Germany.

The Paris-Lyon line is by far the oldest, and is top-speed limited because of how it was traced. (And also because of its out-dated security system that is in the process of being changed)

The Paris-Brest line stops being a high-speed track in Rennes, so even if the first part is fast, it's still a long way to Brest on conventional tracks.

The newer lines are faster, as they are designed for theoretical operational speeds of 350 km/h, with a current operational top speed of 320. (LGV Sud Europe Atlantique, LGV Rhin-Rhone, LGV Est, and even the LGV Bretagne Pays-de-Loire going to Brest)