Time looking into this question as well. There's good advice here. We just used a credit card and had around 100 Euros for the odd thing that didn't accept CC, which ended up being about nothing and we blew it all at the flea market on the last day.

One thing that I read a lot about online was the signature vs pin card readers. I think that is old internet knowledge that just hasn't gone away yet. In France they were certainly all setup for pin credit cards, but they had zero issues accepting a signature on the receipt. We used our card at restaurants, shops, till booths, car rental agencies, etc... With no problems.

Lesson Learned: despite having a JP Morgan Chase office in Paris, there are none Chase ATMs in all of France.

Also, use Uber. And by that I mean always use the app. Some friends of ours just found an Uber driver at the airport and hopped in with him. It ended up being a premium ride and they got hosed on the fare.

Also, make reservations at restaurants. Nothing more disappointing then researching a place to eat, but it not being available. Use Google translate and email, if you can and plan ahead. In Paris the restaurants are small and they book up fast.

Have a great trip!