Player levels and outpacing enemies

Hello kindly pathfinder folks. I am coming from a background in d&d and L5R, I have an idea for a campaign, but an issue I've run into with D&D is how quickly players outpace common NPC types like guards. I have only a passing familiarity with pathfinder, but I think I've summized that because of how the system works enemies are either out paced way more quickly or way more slowly comparatovely, but I don't know which. Can someone break it down for me?