To set up the camera for this scene, set up the tk2dCamera as follows:
1. Native resolution = 640, 960
2. Overrides, delete everything, and click "Add override" to add a wildcard override. Leave this as it is. Don't add any more overrides.
Your game will now scale to fit the screen, the tiled background will reveal more as the aspect changes.
If you want your game to be "pixel perfect", and only ever scale by whole numbers, then switch AutoScale to "Pixel Perfect Fit".
Note, I haven't mentioned anything about 1x, 2x or 4x collections - it really doesn't matter. They are totally independent to the camera. All sprites from platform specific sprite collections should be the same physical size, so for almost everything, you can ignore that feature even exists.
Your question before wasn't related to this at all, or have I misunderstood it? Didn't you want to move something completely offscreen?