Regarding the resolutions:
QC uses a different coordinate system than pixels.
Left edge of the screen is always -1, right side is always 1. So far so good.
Top and bottom edges depend on the aspect ratio of the patch. On 4:3 it's 0.75 and -0.75, on 16:9 it's -0.5625 and 0.5625. So your sprites can fall off the top and bottom of the screen if you change resolutions. You can use the Rendering Destination Dimensions to get access to this data.
When running the patch in Resolume, it takes its resolution from the render width and height settings. They default to the current comp resolution settings, but you can adjust them to anything you want. QC then does the calculating, places all your sprites accordingly and passes the resulting image to Resolume as a texture.
Then you can use the clip and layer width and height to change the scale of this texture. At this point in the chain, this is identical to taking a video and scaling it.
I hope that explains things a bit.