Not sure if this is the right place for this but here it goes anyways.

I have downloaded a couple mods that give me new factions. They are for B27. Problem is I can't use them in Campaign mode without being a different Faction and paying out the rear.

A faction has to be specifically set up to support the built-in metagame as an actual 'Tech' if you want it to be a playable faction. It's fairly simple to set up in theory - go into the faction's Index.ini and add 'Tech' to the module name, then create a Loadouts.ini with all the presets used by the autobuild and AI. Look at the Loadouts used by the Coalition or Ronin for examples.

Unfortunately, the autobuild and AI are finicky, and can bug out if you write the Loadouts file wrong.