Yeah, Having mega Bee would be cool, just made a post in the thread asking to change fire to bug :) as im sure i could build a better Bug/Leccy team then a Bug/Fire team :)
It does indeed mean that. If you have more existing Pokemon of a different available typing, you may want to consider declaring different types (Hint: Bug is available)
For the purpose of the tournament, you'll be restricted to using Pokemon that have at least one of the two types you've chosen.
In a league challenge, you can use any 6 Pokemon, but have to use them for your entire challenge. You can run as many sets on those Pokemon as you'd like, though :D