as in make changes in ePO to only workstations? you could create a set of policies appled to workstations only, and only give ownership to those who need access to those policies. apply separate policies to servers and give ownership to those who can manipulate servers. as far as client tasks, i think you are on your own on that, unless you created an ePO System Tree structure that was basically "My Organization" then 2 equal 1st level Groups called "Workstations" and one called "Servers". You could then assign permissions to one group of ePO admins to the "Workstations" group, and another set of ePO admins to the "Servers" group.
unfortunately you have to do some playing around with it because the permissions arent super granular.
So there is no permission set that says, : access workstation only. ? That would be nice since for some companies the people that manage workstation are different than people for server.