Yes, it is optimal for both to have sound but it still sounds good if you do not. It is not awkward to me.
Different color blades are cool. I have done red and blue before.
I have coupled an Overlord and a Liberator together for a staff. Looked and felt just fine.
Belli to Belli would not be unwieldy if you get 32" blades in your sabers. My archon battle staff has 32's and does great.
Here is a photo of it.