Afaik, UbO will disable JS for entire tabs at a time.

With noscript you can allow the bare minimum number of servers on a given tab/webpage access to load JS, and with a little practice you’ll begin to notice the common ad/tracker domains that seem to want some JS injected in just about every site you visit.

What I want is pretty simple, be able to reboot any computer (ex: work computer) on my USB live system and be able to access my files, my emails

Tails with persistent storage is absolutely a good solution for this specific usecase. It’s designed for it and provides a free and secure encrypted proxy solution (Tor). On top of that, your internet activity will likely help the activists who really need Tor by “mixing” your traffic with theirs.

Tails has thunderbird installed by default, you can connect it to your email account (but do take note that proton only seems to allow 3rd party client integration if you install their bridge app thingy)

If it is your own computer, in your home network, just install the necessary apps on any old distro. Doesn’t matter

I don’t know if it’s a nice to have or a must.

Personally, I’d say nice to have, but it’s not the end of the world if you decide to use something else

NoScript will improve your privacy by a lot, and will make webpages load faster, since it stops stylish and tracker-ridden JS. If a webpage breaks, you can flick a few buttons to temporarily allow JS (or permanently if you’ll be visiting that site a lot).

Tor over VPN is a fine solution if you want to hide it from your ISP, but I don’t think you should install extra stuff on TailsOS. Consider using Tor Browser + UblockOrigin on your own PC over a VPN, it’s pretty much the same thing if you’ll just be browsing online.

Oh-- and one important thing to remember: Don’t expend more effort than necessary for your own threat model. Consider the extent of your privacy needs and act accordingly, going overboard will only leave you tired for not much in return.

P.S.: mander.xyz has a Tor-based onion frontpage ;)