@Nagromme
I just tried my 3000 in native modes (got a CV-64 in there, too) on my NTSC Samsung SyncMaster 150MP (15", 1024 x 768, 30-69KHz H, 56-85Hz V).
1. As far as I can tell, the overscan region does display on the TFT. There is a noticeable border on the edges of the screen.
2. I don't have any overscan pics in DPaintV, but it looks like you'd see the whole thing. The toolbox doesn't sit all the way to the right.
BTW, the "Display Enhancer" does a really good job of translating most of the native modes into a viewable format. Only the Productivity Interlaced mode was out-of-range.