Whenever playing in a public lobby make sure people playing with you actually want to play it modded. Be polite and don't try to force it.
You will be required to boss yourself to be able to set the mod options.
- Find the units unitdefname on https://github.com/beyond-all-reason/Beyond-All-Reason/blob/master/language/en/units.json. For example: for pawn it's armpw.