Since the yaw of the MTi-G-700/710 is referenced by comparing GNSS acceleration with the on-board accelerometers, more movement (when GNSS is available) will result in a better yaw.
The minimal acceleration and movement for the yaw to be estimated is above 7 m/s.
In general, the more accelerations and movement will result in a better yaw. At lower speeds the yaw might be less accurate and take longer. If the velocity is lower, a good option might be to select the GeneralMag filter profile which also uses the magnetometer to stabilize the yaw.
For more information and reference, please see section " MTi-G-700/710 filter profiles" of the MTi User Manual.