Last year it was red/gold vs green/blue and that winner fought the winner of purple/white vs silver/teal.
I was planning to do that again this year, but I don't need to do that. Kurt thinks we should have an 8-way poll for best brigade, and then seed the brigade winners according to the results of the brigade poll. That could work.
Another option is to just randomly pair them. We have some time to decide, since we won't get to the top hero of each brigade until round 3 concludes.
EDIT: for versions, just vote based on which version you consider to be the better one.
If a hero with multiple versions wins the whole thing, we can have a vote on version at the end.
Poll