About " Open RPG-How To DM"

I saw the rule in the simpleRP but there are so many scattered post that I have some problems trying to locate where all of the pieces of the rules are. Also I saw two post on how crits are determined, Caustic says that double digits (11, 22, 33) are crit or crit fails while Eredin says that rolls about 85 are determined. I am....confused x.x

I use Caustic's system myself when I RP as I find it simpler and easy to follow. As long as you and your RP partner agree on the rules beforehand or during the battle, it shouldn't be a problem.