Do I need a 'True HEPA' purifier to clean my air?

Not necessarily. Specialist-community threads we read repeatedly note that filter grade matters less than airflow (CADR) relative to your room size, and one r/AirPurifiers discussion even argues that for recirculating units an aggressively dense filter can move less air. The more important number is whether the unit delivers enough air changes per hour for your square footage, which is why AHAM-verified ratings matter more than the 'HEPA' label alone.