I don’t think you need a general meeting resolution. The committee has a chair, treasurer and secretary. While the contract with a strata manager may include that the SM will exercise many of the functions of those office bearers, those office bearers have the final responsibility to see that those functions are being carried out properly. The SM is engaged to assist the executive committee in its functions, not the other way around. The committee has a function and responsibility to oversee the office bearers and satisfy themselves that the office bearers functions are being carried out properly.
So, if the committee decides that it wants certain of the office bearer functions to be undertaken by those office bearers rather than delegated to the SM, then it can so resolve. Our executive committee has traditionally been more hands-on than most and each new SM has had to learn that.
The SM has a professional duty to step in and advise if they think the committee is not acting as it should but ultimately the buck stops with the committee. If the SM thinks the committee is really going off the rails, the SM would be wise to put their advice in writing to make it clear they did what they could. Ultimately, the SM acts on the advice of the committee, so long as what they are being asked to do is legal. The committee can ask the SM to do any of the delegated functions that are mentioned in the management contract but the SM can’t demand to do a committee function if the committee wants to do that function itself.
To maintain a good professional relationship, I suggest that the committee should keep the SM informed so the SM can satisfy themselves that those functions the committee has taken back to itself are being carried out.