Hi,
There is no such criteria that you filter your demands to be populated based on the planner group at the planning board, however if you define you custom fields populated in worklist profile you might be able to do so not sure need to check on this. As planner groups generally belongs to planning plant which is nothing a planning node in terms of SAP MRS where you can find our demands. It all depends how do you define your organization structure that relates to PM & HR.
Hope this will give you some clarity to you if still need more help please get back.
Br,
Ravi