Look through the configs to change how things spawn, depending on the mods involved, you may have to look at several different files to change everything you want.
ProTip: if you change the pack in anyway, you can expect that people won't be able to help you if you run into problems (like crashes or bugs) down the line. Remember, that the pack devs put a lot of time and energy into the pack, and it's designed to work a certain way.