The guide camera should roughly be pointing at the same patch of sky as your main cam. A few arcmin/arcsec offset does not matter, as long as the mechanical connection between the cams is stiff enough and does not change too much with the moving mount and changing temperature. YMMV.
The guiding keeps the stars on the same position on the guiding cam sensor (average). Small rotations around that set-up can still happen and can become „large“ if your main cam is pointing somewhere else, as we are talking a few micron for a pixel. For large focal lengths and large equipment an off-axis guider can become necessary as the weight and flexure may become so large, that you cannot neglect it anymore and need guide cam and main cam use the same optical train, to correct for deviations caused by these.