Browser containers. Not sure if chrome does it, but Firefox has separate containers that are sandboxed from one another. Make a “Meta” container and only access it from there.

Not really. You have to use browsers that are feature-poor (then again, that makes you ironically again very identifiable). You could use command line browsers that do not leak agents or fonts or stuff like that. Again: Makes you more sus to the ad networks. The best thing - as far as I read about it - is to be a chameleon. Have garbage data that is plausible but vague enough to always stay in a big group of possible profiles. Looks as much as possible like the biggest group of people so you can blend in with the mass, while not raise suspicious behavior. And that continue sly with every request you make to every mainstream website you make. You can see how this is hard enough already. I think there are people out there that might can give you a better answer than me. I try to block as much as possible wherever I go via uBlock Origin and Pi-Hole. But this is only a thin veil. In the end, they have me in their database already since years. But as long as I do not see the actual ad, I hope that I get ranked very low in the bidding process as they must know that I do not see/click those. The average instagram user without a adblocker is much more interesting for them.