No.

The **viewport** is a rectangular region on the **backbuffer** that determines the area in which the rasterzer 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 rasterizer takes inputs in **projection space**, converting vertex positions to pixel positions within the **viewport**. The position (-1, -1) is in the bottom-left of the viewport, and (1, 1) is in the top-right. To actually 3D vertices mapped into projection space, you use a projection matrix.

(`SpriteBatch` uses a particular projection matrix that lets it take input coordinates in client space within the viewport.)

Here are some references about <a href="http://gamedev.stackexchange.com/a/8694/288">the various things that determine display size</a> and about <a href="http://stackoverflow.com/a/3020190/165500">projection space</a>.