This depends on how pro active your committee wishes to be (the more the better for you and your strata scheme).
The SSMA states that the chairperson of the committee has to chair the meetings. In practice plenty of chairpersons request the managing agent to carry out this delegated function but it is first and foremost the right of the chairperson.
Many EC’s will regularly meet without the strata manager present (which can significantly cut costs if they meet often).
In practice a secretary should regularly check/clear the owners corporations mail box and reply to or forward any necessary correspondence as well as posting any notices & minutes on the notice board. If your agent is not attending meetings the secretary should take the minutes and distribute them.
The treasurer will not have hands on access to funds if they are held in a trust account managed by your agent however in many circumstances they would be checking and approving invoices prior to the agent paying, giving investment instructions for any term deposits required and should be regularly seeking out and checking through financial statements provided by the strata manager. It is also helpful for an active treasurer to be involved in the preparation of a proposed budget prior to your AGM.
Hope this is helpful.