How many players can play "team vs team"?

Like the title says, how many players can play "team vs team"? Is it as many players your subscription allow, or does that translate to how many teams that can play?

So let's say you have a free account (allowing 10 individual players), can there be 10 teams in "team vs team" then?

That seems to be the logical answer, but I have found evidence to the contrary. In an attempt to check this on my basic/free account (allowing 10 individual players) I created a "team vs team" game and made teams on my computer. The confusing part was that I could seemingly make as many teams as I wanted. I stopped at 21 teams with 3 members in each team though, as creating more seemed futile.

Why could I suddenly create 21 teams when 10 seemed to be the logical number? What are the rules? How am I going to be able to create a quiz for a 50th birthday party when I'm not even sure it will work? What restrictions will there be if I starting to pay for a Standard subscription?