This is a switch I made yesterday, but instead of Chrome to Firefox, I switched from Vivaldi (Chrome, but kinda like old Opera) to Floorp (japanese fork of Firefox with focus on privacy and sane defaults).
I got Sponsorblock for YouTube, uBlock Origin for ads and Gesturify for those awesome mouse gestures (my main reason for using an Opera-like).
Sometimes, I use Tampermonkey for misc Scripts on different Pages, so I installed that aswell. But for now, no scripts for Tampermonkey, as I primarily focus on setting it up to be more like Vivaldi.
Other addons are Ghostery for more privacy and Session Buddy to prevent oopsies when playing around with Tabs and windows.
Floorp even has dark mode for bright pages already included in the box.