Yes, you can mix and match like that, that's fine.

We do need 3 unique threads. However, as it says up there, if only 2 people reply to your post, we'll take that into consideration if you absolutely can't get another thread, and we'll try to determine if that was out of control. Like, if it was a post locked to only 2 people, that won't count, but if it was an open post and the threads with 2 people are long, we'll probably be ok with that.