I have no significant experience on a C210, but many years operating a TSIO520 on a C206 and C335.
The auto waste gate fully automates and maintains MAP by varying the waste gate setting based on throttle and atmospheric pressure (altitude) Thus MAP will be maintained right up to the "critical altitude" when the waste gate is fully closed and any further climb will result in loss of MAP. From memory this is typically around 18000ft.
The main thing to watch out for on these engines is not to over boost at low level ( typically on the take off run when turbine lag can catch you out)