A useful CMA leans hardest on recently sold comparables, because those reflect what buyers actually paid rather than what a seller hoped to get. Active listings show what you are competing against right now, and expired listings often show a price that was too high for the market to accept.
Adjustments are where a CMA earns its accuracy. A comparable with an extra bedroom, a finished basement, a better lot or a newer furnace is worth more, and a competent CMA quantifies each difference in dollars rather than describing it in vague terms like nicer or updated.
A CMA is directional and free, which makes it useful for a rough sense of range, but it is not a substitute for a walk-through that catches the improvements public records miss. Get your hand-reviewed valuation from Joel Dyck.