We've done the trip from CDG to hotel several ways, public transport and taxi. At that time of day, the roads shouldn't be too busy, so if you can afford it, you might want to choose to take taxi on a day that you will be jet lagged. Not sure about the reference to pickpockets; my only comment is to be careful about pickpockets in any big city, in the U.S. or Europe.

In terms of "small backpack," just don't put anything in it that you wouldn't want to lose or have taken - that's the place for umbrella, jackets, tour books, etc.

Getting train tickets, I don't usually have an issue that all of the machines these days seem to have an English option.

For boat rides on the Seine, I always take the (smaller boats) vedettes du Pont Neuf. I also like to take a trip in the twilight or evening, so I can see the Eiffel Tower at night; I find it magical. So that would be my vote.

If the Michelin Bib restaurant near Gare du Nord is a good memory that you would like to repeat, then do that.

A taxi from CDG to Paris will cost about 60 euros. Taking the train will cost about 25 euros and it won't deliver you straight to your hotel. We are seniors and always opt for the taxi since we also travel with checked bags. IMHO it is not worth the risk of tripping or getting sore muscles from pulling suitcases to save 35 euros, especially since you are planning lots of walking in Paris.

1. I suggest taking a taxi but a dear friend of mine and my traveling companion next month insists on the train for cost and environmental reasons. A taxi will cost you 65€ and the train will cost 26€. It is not difficult to purchase tickets. The challenge that I see for a lot of travelers is making the change from the airport train (the RER) to the metro but if you are going near Place Saint Germain, the walk from the RER to the metro line you will need is only about 5 minutes. If you are going near Place Saint Germain, you could exit the RER B at the Saint-Michel-Notre-Dame stop and walk approximately 15 minutes or change at the Saint-Michel-Notre-Dame stop to Line 4. It's probably about 5 minutes faster to change to the metro than it is to walk. I would walk above ground because I hate walking underground and prefer to walk a bit than to make connections but YMMV.
2. You ay not be in the area and it not completely off the toruist trail because it is near Rue de Martyrs but take a look at Restaurant Caillebotte on rue Hippolyte-Lebas in the 9th. I am planning to have lunch at Le Cadoret in the 19th next month when I am in Paris but I have not been there yet. I mention it because it is way off the tourist trail and I have been told that it is quite good.

For boat rides on the Seine, I always take the (smaller boats) vedettes du Pont Neuf. I also like to take a trip in the twilight or evening, so I can see the Eiffel Tower at night; I find it magical. So that would be my vote.

I agree, plus if you are staying in St. Germain, the Pont Neuf is a lot closer to you than the Eiffel Tower, which is where some of the boats start from. We just got back from Paris about 10 days ago and did an evening cruise with Vedettes du Pont Neuf and it was very nice. I especially liked that we didn't have to walk to far in the evening especially when the cruise was over as it was only a 10 minute walk from our hotel.

FWIW, I was just there (stayed in St. Germain) with my 2 grandchildren. We opted to take the metro from Gare du Nord (we came via Eurostar) but when it came to getting to CDG for the flight home, we opted for a G7 taxi, which really worked well.

There is a very nice restaurant called Au Petite Suisse in St. Germain. It is a classic brasserie frequented mostly by locals that I read about here on the forum, and it was only a few blocks from the hotel. I was very excited to see an array of salads on the menu, and I ordered a wonderful salad with mixed greens, ham, roquefort cheese, walnuts, and pears. My grandkids each had the roast chicken special, which was served with fries and a mixed green salad. We really enjoyed the food and after dinner, couldn’t resist ordering some desserts we saw in the case. My granddaughter opted for the chocolate mousse served in a cute little glass canning jar, and my grandson and I both got the creme brulee, which just melted in my mouth. I recommend it highly.

A fixed-fare taxi from CDG to St Germain will cost €65 for the two of you. No “reportedly” about it — fixed fares have been the law since, I believe, 2016.

Thanks for all the comments. I had been told I’d was €56 but now at least I won’t be surprised . Thanks for comments about the boat trip and suggestions on restaurants.
We are looking forward to just enjoying Paris without trying to see all the ‘must see’s’ as previous trips we tried to do too much.

It's 56€ to the Right Bank but 65€ to the Left from CDG.

We spent three days in Paris earlier this month. We took a taxi from CDG to our hotel near the Eiffel Tower, fixed rate 65 euro. During our time in the city, we used the Metro extensively and saw many people struggling with luggage up and down the ever-present stairs in the stations. As active seniors, we had no desire to take a chance on stumbling down stairs while wrestling bags. It's not worth ruining the trip you've paid thousands of dollars for. The one downside of the taxi was the weekday morning traffic. It took about an hour and 20 minutes to get to our hotel, simply because the traffic was murder.

The greatest risk for pickpockets will be the louvre, the Eiffel Tower, Musee d'Orsay and any time you are on public transport. For transfer when I have all my stuff, I used a money belt under my clothes and then stow valuables in hotel safe or apartment. You are not at greater risk by taking the train to the city.

If your hotel is near an RER B stop then those all have escalators and elevators. If you have to transfer to th emetro -- those all have stairs, sometimes lots of stairs. We use the train when doing side trips with our backpacks as we will on a sidetrip by air to Geneva this May -- but with heavy luggage and I consider at my age 15 kg to be a heavy bag for managing on many stairs, then we take a cab.