If I have Tomato on my main router and I want to leverage one of the alternatives for my secondary router to extend the wireless network [wireless client mode or wireless ethernet bridge mode], does that second device need Tomato on it? Or can I use a different firmware on the second device?
My second device does not support Tomato. So, I could try some other firmware it does support, or get rid of it and get a second device that supports Tomato.
It doesn't have to use Tomato. If you setup the second router as a wireless bridge it should be found fine from your main router.