Our chip and signature credit card worked everywhere. It was very common to see people using credit/debit cards for very small transactions (ice cream cones!). I used our card for purchases over €10 and was never turned down by a merchant. Twice, I purchased a carnet of Metro tickets on machines with the card. At the end of the transaction, the screen said, "enter pin," or something like that. Then, without my entering any pin, the machine proceeded to disperse my tickets. Too simple and, again, no pin was needed.
When we didn't want to take a chance of (yet again) facing long delays in a Metro station, we used Uber to get from our apartment to Gare de Lyon and it worked flawlessly. I put the app on my phone at home and put a credit card with no charges for currency conversion on it.
In spite of what I keep reading on this forum, whenever I asked if we could share a meal, I was always greeted with a cheerful, "Of course." And, our portions often were individually plated. For the record, we were not eating at anything near elegant level restaurants and we were not ordering a fixed-price menu.
I purchased train tickets from Captain Train for four legs over the course of five weeks. One was a print-at-home ticket and the rest were collect-at-station tickets. The SNCF machine at our nearby St. Michel RER station didn't offer a way to retrieve then, but Gare de Lyon had numerous machines to collect your tickets. It worked like a charm. I had planned to pick them up at CDG airport, but, due to train strikes, we had arranged for a driver to pick us up, so no side trips to the ticket machines. The bottom line is that it's quite simple, but might not be available at smaller stations.