No, the two aren't alike at all. The only parallel is maybe in terms of growth and popularity. I've noticed that NixOS is quickly gaining popularity among a lot of long-time Linux users, maybe in a similar fashion to how Arch did, but for completely different reasons. They aren't alike at all.

Still Arch on main desktop, but slowly moving towards NixOS everywhere.

That mindset unfortunately leads you to being locked into vendor-specific ecosystems with no control about the software you're using. The big vendors (MS, Apple) know this and have already started extracting more value (in form of data) from their users. Next step will be to put more stuff into their clouds and sell you a subscription. You'll be renting software with included spyware then. With zero control yourself. Linux and FOSS gives you control back. It's also quite easy to use in 2023.

https://github.com/libre-tube/LibreTube refers to https://libre-tube.github.io/
Any other site is probably a scam.
Invidious is nice but it probably leaks your IP address to Google/YouTube, which you don't want when using a privacy-friendly frontend for it. Especially not if you use your real IP. The Piped frontends, on the other hand, don't leak your IP to Google/YT.

Highly unlikely. A site could try to exploit unpatched security holes in your browser, but if your browser is up to date, this is unlikely to succeed. Modern browsers are very complex and large so they have lots of weaknesses, but they also get fixed quickly, a lot of eyes are on their code and they utilize sandboxing techniques as well to isolate things from your system.
Still, it's a good idea to harden your browser further yourself, or run it in an additional sandbox.

Check Flatpaks as well.

I don't like that analogy because the CLI tools offer more power and features in configuring your system than the GUI does. GUI never offers the full range of options. Designing GUIs takes a lot of time, which leads to skipping features. No GUI installer can offer what you can do "by hand" in the console during setup, for example. E.g. the partitioning and filesystem stuff is always quite limited in GUI-based setups. GUI and CLI complement each other and every1 should learn a bit of CLI as well

Technically there are still workarounds like disconnecting from the network or editing the installation sources, but it's still anti-user and worse than in older versions. Win will continue to get worse over time. Look at a freshly installed, default W11 Home consumer desktop for example. What most people probably use. Just open the start menu. It looks like the OS needs an exorcism first, before you can use it. But maybe many people have already become used to things being this bad