Metal supports multiple optimizations that you can use to increase the performance of your application.
Metal supports memoryless render targets which enables you to render to a RenderTexture without backing it up in system memory. Unity only stores the contents temporarily in the on-tile memory during rendering.
Metal supports memoryless render targets on mobile devices from iOS and tvOS 10.0, and desktop devices (including Apple silicon) from macOS 11.
For more information, see RenderTexture.memorylessMode.