Do I need a separate power adapter for a wireless charger?

Often yes. Several picks here, including Anker's 313 pad and many of the MagGo stands, ship without an AC adapter, and a few require a specific higher-wattage brick (commonly 20W-30W USB-C) to hit advertised speeds. Reviewers repeatedly flag that buying the wrong low-wattage adapter is the most common reason a charger feels slow.