You can set the bold font like this:
(But I'm not really convinced "that the Computer Modern Sans Serif demibold condensed fonts are an adequate substitute" as claimed by the faq.)
The main new feature in TeX Live 2020 that I actually use is the HarfBuzz renderer integrated into luatex. If you answer a lot of questions on TeX.SX, though, you’ll definitely want to test your MWEs on the latest version.
In general you need not update to the newest ("vanilla") TeX live if you are happy with your current TeX system. Many packages in the TeX world have been stable for years (the popular citation package natbib for example has not been changed since 2010), some others will only have received carefully crafted, small fixes for very specific bugs.
But there is a ...
Well, that's really up to you.
Personally, I install texlive always from the installer script. (https://www.tug.org/texlive/)
I never use the default packages. In particular, on Ubuntu, they can be quite old.
Having said that, I only update the installed packages if there is a bug that affects me, or there is a new package that I need.
In general, ...