When importing Spond groups to Spond Club, ordinary members will not notice anything when using Spond, but group admins might see their access rights changed, depending on what their new roles have been set to. See more under Roles.
If you get duplicated members in Spond Club after importing the group, it is important that you merge them rather than delete them. Deleting them will cause them to lose access to the group. If you merge them, all group access will remain.