I don't think Rick Steves is best for Paris/France, but I did use him for Switzerland. I think he does some areas better than others. However, even though I don't use him, I agree that for total beginners, which the OP is, I think he can be very worthwhile.

I don't agree that everyone has to take a taxi, it depends on how much baggage you have and where you are staying. Mass Transit is much better for the environment and a lot cheaper. IN this case, though, it depends how used to public transit (bus, metro/subway, etc) the OP already is.

AS for baggage, checking baggage has no effect on how long it takes you to get through "customs" and immigration in Paris. none, unless you are maybe bringing in something illegal and a dog sniffs it or something. Paris doesn't really have obvious customs (unlike some countries where it's quite noticeable, like Mexico). If you are bringing in lots of money or business products, etc., things you'd have to declare, you sort of self-report at a desk over to the side. Anyway, checking bags doesn't have anything to do with how long it takes to get through border control (immigration). In fact, you don't even get your bags until after that, just like in US. I always check a bag for trips to Europe and in Paris, the bag is always already out in the baggage collection area after I get out there past immigration.

Having said that, sure, I agree to try to pack efficiently and not take too big a bag. IMO, too big would be anything over 24 inches. You may not be able to carry aboard a bag of 21-22 inches, either, depends on airline and how crowded they are. I've had bags that size confiscated at the gate sometimes (and checked, which is ok). If you are taking a train, you'll need to handle that yourself at times (going up the steps, etc). I can handle a 24 incher myself, but you know yourself. And don't put in a lot of heavy things like bottles of shampoo, appliances, etc. I hate to be obvious, but I"ve actually seen people on trips who pack full bottles of regular size shampoo in their luggage! I'm a minimalist and only pack travel size of a few things. But I have dry hair so don't have to wash it often, and don't use any hair appliances, and use minimal cosmetics.

The only things you need to work on first are the dates, flight and then hotel. Attractions may need to be booked/reserved, but that's the last thing.

The old saying used to be "Take half the luggage and twice the money".

The luggage part is still good advice, but money is less of an issue now that the world is moving towards contactless payment (and if you really need cash, you may well be able to use your cards in local ATMs). Still, you should check with your bank/card issuer about their rules and charges. Others will be able to advise about cards specially designed for overseas transactions.

And do familiarise yourself with public transport:

https://www.ratp.fr/en/visiter-paris
https://www.parisbytrain.com

(And plenty of videos on YouTube - for one check out paristoptips)

What do you mean by transpiration? I only know this as the French word for respiration but I think you know how to do this already...

Lavandula

Transportation? Auto-corrected???

Lavandula

A few thoughts:
1. For your possible 2nd destination, what interests you? Would you like to see a city like London, get into the French countryside, take a train to see the Alps? Lots of options.
2. If you do see two different locations make sure to check the cost of a multi-city ticket. People often think it's cheaper to do round trip in/out of the same city, but then don't realize the time and money involved in getting back to the initial city.
3. Absolutely agree with using a carry-on and a backpack. Wash clothes once in the middle if you need to.
4. I've only read a few Rick Steves books...but would HIGHLY recommend his videos. They're great for getting to know a place quickly. He's got several on Paris with different focuses.
5. Don't fall for the "skip the big tourist things...you'll be back". I've done the Eiffel Tower 3 times and loved it each time. If you've never been to Paris don't feel bad about being a "tourist"
6. Don't skimp on a hotel by staying further out. Spend a bit more and be right downtown. I'm not enough of an expert to highly recommend one arrondissement over another, although for our last two trips we stayed in the Latin Quarter just south of Notre Dame...and loved it.

Your first step should be to set a rough budget. Figure out what you're willing to spend on this trip. Once you have an idea of what you're willing to spend, start looking for airfare - keep in mind you'll only be able to see out 330 days in most sites, but you can at least get a rough idea of what that budget might look like. Same thing with lodgings.

As for your trip, if 7-8 days is Paris AND another location, you will be reducing your time in one or the other place substantially, which could also impact your budget. If you want to know ideas of what to do or see, I'd look at the Paris Museum Pass: https://www.parismuseumpass.fr/en to get an idea of many of the sites and places available (except the Eiffel Tower) to see. Personally, you could easily spend 7-8 days in just Paris with a day trip (or two) to places like Versailles or even Fontainebleau and not visit a second location. The pass also will give you a pretty decent understanding of the costs (to help with your budget.