All of my games denote which system - if any - I will be using. I make sure to make such things plain. But the last question is odd. To me they are one and the same.
Just in case someone else is having this problem, I'm going to add some clarification to Cassandra's post.
There are some people that roleplay with a very 'fixed' idea of how the RP will proceed - not only for themselves, but for their partner. They have a particular vision, but want someone else to write that vision with them. At the other end of the spectrum is the person who has no
idea how the RP will proceed. (A good example would be a 'pairing' request.) This requires maximum input from their partner as far as negotiations go.
Both extremes can have their frustrating aspects, and most successful ads fall somewhere in the middle. This isn't to say that the extremes can't
be successful - good brainstorming sessions can turn a simple pairing idea into a plot that both writers can sink their teeth into, and throw an extra twist into a more scripted idea.