You can change the delay of them spawning like for example if you want to make them spawn every 5 minutes you have to edit the load.mcfunction and tick.mcfunction files where it says timer 9600 so change that to 6000 if you want them to spawn more frequently (once every 5 min) so basicly 1200 ticks = 1 minute. I made them spawn every 8 minutes because its pretty hard i tried every 2 minutes then every 5 minutes they will just spawn and kill or almost kill your character because after 5 min most players are still on stone gear and no food so thats why i chose them to spawn every 8 minutes so players have some time to get food and stone gear atleast and maby get a shield or other iron eqqipment if youre lucky. Trust me its not that easy try it for your self its verry challenging untill you get like full half iron and diamond armor then they will start doing less damage.