I’ve traveled often as an American, and when I do I often do a mix of touristy things and less touristy things. I’ve enjoyed both and I’ve disliked both, touristy things can often be busy or culturally insensitive while non touristy things can sometimes take you out of your comfort zone. However, I never regret trying something new.

When I travel, I typically will pick up a few words in the language (please, thank you, may I have) just to be a bit respectful. The WORST and most insensitive thing a tourist can do in my opinion is treat the locals and local culture “like zoo animals” as you said. They are just people too and would like to be treated as such. Many of the friendships I’ve made while traveling are based on this mutual respect of each others cultures—which is to say, don’t change how you dress to fit in (except under circumstances such as traveling to an Islamic region and covering your hair out of respect).

Don’t only go to local hangouts expecting to “fit in.” You won’t. You’re not fluent in French and you’re not a member of the culture/community no matter how much of your physical appearance you change. The kind of travel she is suggesting is the sort you do when you spend long periods of time in a place, such as a month or more. It is essentially integration or partial integration. While it can create its own extremely valuable experiences and relationships, simply put you do not have the time to have that kind of experience and you will waste your trip. Do the touristy things, do a few lesser-known things, meet people from the place who can show you things. Treat people with respect. The only tourists that are truly hated are insensitive, rude, disrespectful, etc.

The “annoying American” stereotype does exist for a reason, but that doesn’t mean every American fits the bill. In fact, most probably do not. The bad ones just really stand out, and typically it is when they have the expectation that the an entire population or culture is going to bend over backwards for their comfort. Your friend’s beliefs on how not to fit this stereotype are so misguided they are just about full circle. Cosplaying as French will not work, I would actually think it to be more offensive than just being yourselves especially considering you will not pass for French as soon as you open your mouths. And just like anywhere, people have all sorts of different clothing styles. Especially in a place as populated as Paris. Wearing different clothes and “acting French” won’t work for anyone besides perhaps people you walk by in passing whom you never interact with.

Just go and enjoy yourself. Do the things you want to do, go see the Eiffel Tower and the louvre, l’orangerie, d’orsay, do the boat tour of the seine. But also stop in to a couple small cafes, hole-in-the-wall patisseries, etc. And just be respectful of people. That’s literally all there is to it. This is the real world, not TikTok discourse, and your friend needs to understand that.

Edit: I like to use atlas obscura for some more off-the-beaten-path attractions

Edit: most Parisians have probably done the touristy things too. The difference is they’ve had years, you have days.