In the graph you have speed on y-axis and meter on track on x-axis.

Exact. More precisely, on the X axi syou have your position (in meters) with respect to the track centerline.

So when you take a different trajectory (which may or may not have a different speed) you also may have a different position on the track centerline (specially in low speed corners).

The trajectory is important but you cannot describe it in a graph.

With a proper telemetry analysis tool you can. It was possible in what random did (and, unfortunately, is no longer available).

You had a track map with your trajectory (for all the laps under analysis) and "normal" graphs with speed, throttle, brake or whatever.

So you can look at the same time at speed and trajectory.

You can for sure describe the speed during the lap.. higher is the speed also in a curve, best is the lap time.

Unless the fact of taking that corner at an higher speed makes you take the next one at a lower one

MaX.