GLCanvas ZoomToFit depends on object size and control size, trying to match both for the object to be totally visible, having the object in the middle of the control. This means that if the object aspect ratio doesn't match with the control one, the zoom is less perfect.
About the other modes that you indicate, they are not implemented.
This control is halfway to the control I wanted, rendering not only mesh but surfaces, and having not only zoom, but scroll, like UltimateOpenGL got. Unfortunately I haven't had time to support the author of this interesting control.