To allow a user from the ``group_backend_ui_users`` group to interact with a specific model you can either add an access rules to this model for ``group_backend_ui_users`` or you can add ``group_backend_ui_users`` to the ``implied_ids`` of a new specific group.

The Backend groups are from the "User types" category (``base.module_category_user_type``), the same category as "Internal User" (``base.group_user``), "Portal" (``base.group_portal``) or Public (``base.group_public``). Be aware that a user can only belongs to **one group of this category**.