The row height is automatically set to fit as many rows on the screen as possible, with a minimum row height of 30 points. However, it is possible to alter the row height based on the custom content inside. To do this you would need to implement the GetRowStyle method on your SGridDelegate and return a SGridColRowStyle object with the size property set appropriately for the content.
As for the columns, if by auto resizable you mean based off the content width, you do this using the same method as above but instead by implementing the GetColStyle method on your SGridDelegate. Also, you can set a property on the grid to allow the columns to be resizable by the user, using a pinch gesture.
I hope this helps you!