Adventure on my own mostly following Rick's guide's. Two items of clothing not to be without: fleece jacket & my Marmot rain jacket, which packs down to nothing and rain never gets through. Spent less €300, could use debit/credit nearly everywhere with minimal to no fees. Stayed in Cobblestone AirBnb Paris, was great and very reasonable.
Signed up for 'Paris Greeters' the experience was superb! Same day went to Louvre (cold rain, absolutely no line), but I have major art background and would not waste time to go - too many people, can not enjoy or see Mona much less the other major artists. I am 67 and 45 years ago was able to sit and view, no longer possible. Spend your time at the Orsay & Rodin. Take the day trip to Chartres, lovely. A true pilgrimage.
Half the folks use backpacks. I never had any concern regarding safety nor pick-pockets. I believe most thought I was not a tourist, just local. Used the smattering of French I learned before my trip. Everyone was nice to me and helpful when needed. Challenge of a different lanuage was fun, since i was on my own, sort of a French immersion course. Sure miss the bakeries!