[o_O]

So you want to check whether your script can make a server laggy and need players for that?

I think the NPCs would work the same way as long as they trigger your scripts. I mean, I'm not sure what sort of gamemode you're coding but if your script does something when a user enters a car, you're going to have to make your NPCs enter a car...

So that might actually be a lot of work. You may as well consider getting a few volunteers to test your server out. I've done it before. Just make your server public and you'll get a few people. You could also make an announcement on the forum asking for help.