The board does not "provide the managementguidance". Nor do shareholders.
You are confusing the chain of accountability with chain of leadership. Leadership stops at the CEO. Accountability goes up through the board and back to shareholders. What you call "guidance" (determining what the company will do with its resources) is a function of leadership. Leadership is a job skill required by management, and the top manager is CEO. Leadership ends there. The board's job to is make the CEO accountable for providing effective leadership. Leadership is not the board's job, because the board delegates that responsibility to the senior management.
While the board oversees corporate governance, that is the very framework of rules and policies that govern both the board members and senior management. For example, stating who is accountable to whom is described in the governance guides. Apple's governance rules (which are typical for US corporations) gives the CEO (and not the board) authority to (1) lead and (2) speak for the company. Governance recognizes no higher authority with respect to leadership of the corporation.
As for whether the board members "represent the views of the shareholders" is something that is entirely up to the shareholders, since that may or may not factor in when they vote on reelecting board members. However, the views of the board members and the views of the shareholders are irrelevant because Apple's governance policy give Tim Cook the final authority to speak for Apple. Further, it does not require Tim Cook to heed the personal views of any board member or shareholder; he merely has the autonomy to choose to do that.
That's all true. However, there are a couple of things you left out:
The board can influence the CEO's leadership in at least two ways:
a. The board can approve resolutions that require specific actions.
b. The board can, of course, hire and fire CEOs. So if the CEO is not acting upon the Board's guidance, they can fire him.
In practice, a CEO who ignores the Board's direction doesn't last long.