Multi GMs questions

In theory (and again there are probably edge cases here we haven't found yet), the two GMs can act completely independently of one another. So they can be on different pages interacting with different objects etc. Really the only problem that I can foresee is actually the opposite -- if the two GMs try to modify the exact same property of the exact same object (e.g. change the health on a token at the exact same time). It will still happen, it's just that one GM may overwrite the other's changes on accident. But as long as you're not doing that, in theory it should "just work" fine :-)

And I should also point out that there's no limit to the number of GMs -- so if you play a very communal game and want all 6 players to be GMs, go for it!