Hello,
Please check ours simple Membership only help for you connect some product from Virtue Mart to some Joomla User Group or to many Joomla User groups.
Next you self in every Component may set what some user group can do.
Also in Joomla User Manager: exist Access Levels menu, there are you also may create new Access level and in every Joomla component set permissions for that "Access Level"
If you need have some Joomla group what will have access to both Joomla group 1 and Joomla group 2, best create 3 product and 3 member group in Simple membership
Thanks,
OrdaSoft team,