Concerns about the Ranking System

With the new ranking system, many people are waiting to see how the quality of games will be effected by the splitting of ranks to your roles. I had a few concerns of my own that would be nice to get answered.

1. How is matchmaking actually implemented? Do you use the lp of the role you queue up for? Or does the matchmaking simultaneously look for all 5 roles at their respective mmrs?

2. Recently, I've found myself enjoying queuing up for fill quite often, it helps me with my tilt and makes the game more enjoyable for me. That being said, I haven't done extensive math on it, but it seems like that would be detrimental to climbing if that was how you wanted to approach the ladder.

3. I haven't experienced it myself, but I see a lot of complaints on reddit and twitter about people getting into games with people that were autofilled and ended up inting so they could go next faster and get their main role, with less of a punishment that would have been if the "splashing" system wasn't in place. How is Riot looking at tackling this?