How can I modify the Firefox defaults?

Question

How can I modify the Firefox defaults to contain a few Add-ons?

# NoScript
https://addons.mozilla.org/en-US/firefox/downloads/latest/722/addon-722-latest.xpi

# HTTPS Everywhere
https://www.eff.org/files/https-everywhere-latest.xpi

# Privacy Badger
https://s.eff.org/files/privacy-badger-latest.xpi

# Cookie Whitelist, With Buttons
https://addons.mozilla.org/firefox/downloads/latest/6875/addon-6875-latest.xpi

So if there will be a new user on the Desktop machine, starts Firefox, it will have the mentioned given Add-ons.

The OS is a RHEL Desktop.

Answer 1

There are a couple of ways...
1. You can use the same log in credentials for both PCs and you will get everything synced. This is the way I prefer, even though it would be better that they included also an option to sync (or share) with other users (say addons). Of course, you can choose to sync only the addons for your profile.
2. Using an addon with witch you can back up your addons, and then "restore" them to the other PC, such as FEBE.
3. You can modify the package and the database if you can, so they get preinstalled (something that I find very complicated).

Although not all where entirely what you requested, these are some of the alternatives. I will gladly edit the answer if someone else knows some other way.