Where are Theme List details located?

I tried running a search in the subreddit and didn't come up with much.

Where can I find detailed rules for what models are allowed with each theme, and what benefits are gained for fitting within those restrictions?

As far as I understand it, they are contained in the War Room app, but I don't have much interest in spending money on the app so I'm wondering what my other options are for keeping up and staying relevant.