Except as provided in subsection (b) of this section, an adult may voluntarily, without undue influence or coercion, enter into a supported decision–making agreement with a supporter or supporters. If a person under guardianship enters into a supported decision–making agreement under this title, the agreement does not supplant the authority of a guardian of the adult, unless the court authorizes the limitation or removal of guardianship due to the existence of a supported decision–making agreement. A guardian may not prevent an adult from entering into a valid supported decision–making agreement that does not supplant the authority of the guardian without good cause. A supported decision–making agreement or any provision of the agreement does not: Supplant the authority of an agent under a power of attorney executed in accordance with Title 17 of this article or an advance directive executed in accordance with Title 5, Subtitle 6 of the Health – General Article; or Supplant or grant authority or agency powers contemplated by a power of attorney or an advance directive. If an adult voluntarily enters into a supported decision–making agreement with one or more supporters, the adult may authorize a supporter to provide support to the adult in making decisions in areas of the adult’s choosing, including: Gathering information; Understanding and interpreting information; Weighing options and alternatives to a decision; Understanding the consequences of making or not making a decision; Participating in conversations with third parties with the adult’s explicit authorization; and Providing the adult with support and advocacy in implementing a decision. Nothing in this title or the existence of a supported decision–making agreement may preclude the adult from acting independently of a supported decision–making agreement. The availability of a supported decision–making agreement is not intended to limit the informal use of supported decision making or to preclude judicial consideration of informal supported decision–making arrangements as a less restrictive alternative to guardianship. Execution of a supported decision–making agreement may not be a condition of participating in any activity, service, or program.