No.
The viewport is a rectangular region on the backbuffer that determines the area in which the rasteriser draws pixels. A viewport (X,Y) of (0, 0) is always the top-left corner of the backbuffer (in XNA). You can freely move and resize it within the backbuffer.
The backbuffer is the underlying surface that the GPU is drawing to. To resize it you have to reset the graphics device. It doesn't have a position of its own - it is drawn on whatever window it is attached to, using that window's position (in this case, a panel counts as a window).
When rendering, the rasteriser takes inputs in projection space, converting vertex positions to pixel positions within the viewport. The position (-1, -1) in projection space is in the bottom-left of the viewport, and (1, 1) is in the top-right. To transform the 3D vertices in your world into projection space, you use a projection matrix.
(SpriteBatch
's default projection matrix lets it take input coordinates in client space within the viewport.)
Here are some references about the various things that determine display size and about projection spaceprojection space.