The Grid can be used with only one row and one column. You can certainly use it along with the ZIndex property to control ordering.
A Canvas could be used in the same way. Grids are good when you want the content to size to fit in some way (like adjusting a child's size based on the parent by setting margins for example). A Canvas is absolute -- the content (children) won't size to fit and always appear where you specify them, relative to the Canvas upper left corner.
Whereas the grid can size to fit the children, a canvas does not.
A canvas, all things being equal, should be faster as it doesn't do any calculations for sizing, etc. It just places the children as specified, or defaults to 0,0.
A Canvas could be used in the same way. Grids are good when you want the content to size to fit in some way (like adjusting a child's size based on the parent by setting margins for example). A Canvas is absolute -- the content (children) won't size to fit and always appear where you specify them, relative to the Canvas upper left corner.
Whereas the grid can size to fit the children, a canvas does not.
A canvas, all things being equal, should be faster as it doesn't do any calculations for sizing, etc. It just places the children as specified, or defaults to 0,0.