Your wheel magnet speedometers must be calibrated. Usually lay out a tape measure that is long enough for a couple of wheel revolutions. Weight the bike, and roll out the distance traveled in a couple of turns.

I still have difficulty getting the accuracy greater than about 1/2 cm. And, as the tire wears, it should get smaller, but I've also had difficulties verifying as it falls close to the limits of my measurements.

What about those micro swerves one makes with pedaling, and to keep the bike upright?

Still, I'd trust the magnet based sensors over Strava. I have one ride were I accidentally left Strava on overnight, and got about 300 miles and 14,000 feet climbing for doing nothing.

I do think Strava and RWGPS are close on distance. Give or take a couple of percent. Climbing is much more difficult to calculate, and one sees widely varying estimates.