There are some acts an agent can never do for a principal even if the power of attorney says the agent has authority, including voting in an election and making or revoking a will. A full list of prohibited acts is available at Florida Power of Attorney Act Section 709.2201(3).
Some powers can only be granted if the principal signs or initials next to the power in the power of attorney. These powers include making a trust for the principal and changing beneficiary designations for the principal. A full list of acts that require an additional signature or initial next to the power is available at Florida Power of Attorney Act Section 709.2202.