How does one start a commerce game, and how do mods work?
Alternatively how Luddite friendly are mods?

I know I would need to be a member to do mods, do you also need to be to make commerce games?

You don't need to be a member to create or join commerce games.

See https://www.warzone.com/wiki/Mods to learn about different mods and how to make mods.

How do I create one then? I cannot find any box to check to create a commerce game when in game settings.

Click "Change army settings" and you'll see a checkbox named "Commerce"

I guess you need to switch to unity