As far as I know there is no way to easily list all permissions a group has, since advanced permissions really is advanced. You can set up permissions on so many objects, pages and tasks that I think the list would be somewhat incomprehensible.

I tend to use very defined groups (with clear descriptions) and use groups, group sets and in some cases group combinations to achieve the permission settings I want.

I suggest you try to put it all on paper and define what kind of rolls your site needs and what each roll should be able to do. After that you can create the groups needed.

Thank you for your help.