You could definitely create a forum for travel (named whatever) - and indeed if you did you'd be the beneficiary for that specific forum. From there it would be up to you to manage that community and foster it's growth, which would determine the rewards flowing through that community.
Keep in mind though, that only posts made through chainBB, and through that specific forum, are eligible for beneficiaries. The tags and topics aren't going to be what make or break a forum - it will be the community behind it and how it's built.
I also don't think that all the popular tags on Steemit are going to make a good forum. I think some of the best forums we'll see in the future are tags that have done absolutely terrible on Steemit (just because Steemit isn't designed for all content).
As for subforums - I'm not sure how the beneficiaries will work for that yet. I'll try to come up with a system that's fair.
Thanks, I'll be in contact.