IMO the only real difference is using Invidious

Front-ends circumvent YouTube’s algorithmic recommendations.

And that’s huge. I find the algo to be addictive and toxic. Even if you’re behind nested Tor relays or whatever, and YouTube can’t track you in any way, it deprives YT of the opportunity to short circuit your brain, and keep you scrolling.

But in reality, browser extensions are imperfect, and browser YouTube is still getting tons of information on what parts of videos you watch, maybe where you stop scrolling or pause your mouse, what resolution you stream, whatvideo you choose next and so on. Even with obfuscation, and an ephemeral profile, I bet it’s enough to fingerprint you.

If you want to circumvent this, try a browser that goes hardcore with anti fingerprinting specifically, like Cromite. These go out of the way to fake anything identifying, like (for example) returning fake core counts, screen resolutions and such. Then load that up with UBlock and more YT extensions.

Software developer here, while I do not know everything about it, from what I observed and learned is following the case:

• NewPipe has a component called NewPipe Extractor which is also used by most other opensource YT clients like LibreTube. From what I observed, it extracts the video URL for the stream without rly loading anything else of YouTube.
• When you use YouTube in a browser, the entire YouTube page is loaded minus the content that has been blocked by Brave Shields, uBlock Origin or other utilities.

I think privacy and security wise there is not a lot if not at all a difference, as both take a best effort approach to limit YT’s ads and tracking mechanisms.

The only real difference is if you log in via e.g. Grayjay and on the website directly. Grayjay will only use your token to authenticate while necessary and not share all kinds of data with YT, while the website stores your watch history, search history, etc.

It shouldn’t be a difference, what Ublock and Brave and network based blockers such Pihole do is they have a list of domains that are not allowed to load on your system.

If they find that www(dot)adexample(dot)com is trying to load in your browser, they simply block it and the video continue.

Maybe the only different is the privacy itself that offer something like Libretube vs something like YouTube + Ublock. While using Libretube, you are only loading what is neccesary, you are not giving Google more information that you shouldn’t, and while you using YouTube in Firefox for example you are loading all the cookies, trackers and that stuff, even in private browser with maximum privacy settings and adblocker.