Except as provided in § 5–3B–27 of this subtitle and subject to subsection (c) of this section, before ruling on a consensual adoption petition under § 5–3B–20(b)(1) of this subtitle, a court may order a court investigator or child placement agency to conduct any investigation that the court considers necessary. Except as provided in subsection (c) of this section, before ruling on a nonconsensual adoption petition under §§ 5–3B–20(b)(2) and 5–3B–22 of this subtitle, a court shall order a court investigator or an appropriate child placement agency to investigate and submit a report that includes summaries of: the prospective adoptee’s emotional ties with and feelings toward the prospective adoptee’s parents, the prospective adoptee’s siblings, and others who may affect the prospective adoptee’s best interests significantly; and the prospective adoptee’s adjustment to: community; home; and school. If a prospective adoptee is an adult, the court may order an investigation under subsection (a) or (b) of this section only for good cause shown.