I spent 13 days driving around the Peloponnese in October 2022.
The main highway all the way to Kalamata is in very good condition and surprisingly not much traffic especially the further south you go.
There are numerous toll booths along the way with prices varying at each one.
The toll booths I encountered were either manned or unmanned. The ones opened had a large green X sign and the ones that were manned had a human figure sign. Very easy to pay using various means.
Once off the main highway you'll be on secondary roads and back roads. Due to the terrain such as mountains, coastline, going through villages it will take you longer than you think so plan to spend more time getting from point A to point B.
If at all possible I would highly recommend driving through the Langada Pass if you want some of the most spectacular mountain scenery in the Peloponnese. You can pick it up by going from Kardamyli to Kalamata and then east toward Sparta.
Regardless of the route you take it will be a long drive, maybe longer than what some on-line maps say.
I would also recommend some navigation system where ever you drive in the Peloponnese. I used Google Maps and for the most part got me where I wanted to go.
If interested you can read my trip report and photos from another forum:
https://www.tripadvisor.com/ShowTopic-g189483-i1277-k14200587-Peloponnese_Trip_Report_Sept_25_Oct_12-Peloponnese.html