It is possible to unlock about:config preferences in Firefox forks. This is done at the installation level, so it is not customizable per-profile.
I will be using Zen Browser as my example here, but this works in other Firefox forks as well.
First, navigate to your installation directory (e.g., C:\Program Files\Zen Browser). In this directory, create a text file and give it the .cfg extension. In this example, I've named mine zen.cfg.
Type // on thee first line, then for each pref to unlock, add a line with "unlockPref("example.prefname");", replacing example.prefname with the name of the preference you'd like to unlock.
If you'd like to set a default value for that preference, you may do so by adding a line with defaultPref("example.prefname", value);, replacing value with your desired default value. You may use // at the beginning of a line if you'd line to add comments
Here's my example for unlocking URLbar suggestion preferences in Zen Browser:
// SKIP THIS FIRST LINE