Guild Wars 2

I have the +5k rank points item you get from preordering but I never used it because I was worried that it would just put me up vs people who are much higher rank then me. Is matchmaking based on rank points or is that just like a currency or something?

Those are complete different things.

MMR != ladder points != personal pvp rank (rabbit to dragon)

I think it only increases your own personal pvp rank.
Edit: Back in the days it gave glory, but that currency does not exist anymore.

Matchmaking is mainly based on mmr and only to a small part based on rank, but 5k is nothing to worry about. In higher ranks 5k is only ¼ of a single rank.

Formula
MMR = (W/L) * Rank_points + Glory/(Achievement_points + Laurel*2)^2