Default Generator ?

Can I make it so EWG is not the default generator?

If not, is it alright if I were to unload EWG, create a normal world, then load EWG back in? I'm just worried that some problems would occur such as -"Leaves wont decay correctly, Mobs won't spawn correcltly, Lag issues can occour due to the issues listed above." Basically the problems that would occur if I was to generate a world with EWG then remove the plugin.