A 35-year-old woman with generalized anxiety disorder asks her PMHNP why her current benzodiazepine causes significant sedation and muscle relaxation in addition to reducing her anxiety. The PMHNP explains that traditional benzodiazepines are non-selective positive allosteric modulators at GABA-A receptors. The patient asks whether more targeted approaches to GABA modulation exist. Which of the following best describes the relationship between GABA-A receptor subunit composition and the pharmacological effects of benzodiazepines?