Is It Possible to Create an Entity That Stalks the Player?

I've been working on a mod for a few days that adds in an entity that is supposed to follow players from a distance but not attack unless hit. I need help getting it to actually follow the player instead of just seeing the player and wandering off. Also, what is the players walking and sprinting speeds? I'm making several mods with humanoid entities and need to know what to set their speed as. If y'all don't know, that's fine too. I can just experiment with the speed and find that out on my own.