Still, inductive current measurement with the sizes of the clamps they show and typical currents they're measuring isn't accurate at all. Not even considering that voltage measuremens via a wall wart would depend on what load is currently sharing the same wiring.

This might be my bias since I design similar stuff for solar offgrid, where a percent or ten off are that much in capex divided by battery lifetime, then multiplied by battery cost. It bites.

I don't trust inductive clamps at low currents. I would never trust measuring voltage on the same line as a load.

Hall sensors or current shunts; voltage dividers - all driving MCU ADC channels via optoisolated opamps. Everything measured as near to the source as possible. Otherwise you're getting nearly worthless data.