A fast way to edit multiple groups at once is:
Then in the next window, Ctrl select the groups you want to edit and choose "Properties". Here you can go to Group Members -any members you remove here will be removed from all groups you selected in the previous step.
One tip, your changes are not committed to the database until you hit the save button.
Is the Folder check box referring to the epdm folder that the permissions for that group are assigned?
Yup...and also that folder's sub folders.