New user: what settings are safe to change?

Are the settings in about:preferences safe to tailor as per my liking (add a new search engine, disable auto scroll, smooth scroll, etc)? The stuff in the Privacy & Security section I know not to touch other than the .onion services setting and the Security Levels, and I think the Connection section is also safe (looking at quickstart and bridges).
Also, I know not to install other extensions but NoScript, should I leave it at default or is it possible to fiddle with it? Actually what is even the point of it when there’s Security Levels already implemented? And also, is there a correlation between those Security Levels and NoScript?

Also is it safe to add and use bookmarks in the Tor Browser?

I could find answers to these questions elsewhere but I’ve read so many different ones that it’s hard to chose who to believe.