Depending on which lens you have and in which orientation you have it depends on how far you rotate it. I usually aim for between 25% and 33% so if you find out the horizontal and vertical field of views of your lenses (HFOV+VFOV) then the amount you need to turn them is 2/3 of that value
For example the 24mm lens on a full frame camera has a HFOV and a VFOV of 74° and 49°, so you would turn it 45° and 30° depending on the orientation and would get 8 or 12 frames.
Nodal Point is one of those phrases which is wrong but wont go away, it's more accurately described as "point of no parallax" which even explains what it is. As rob says, the PONP is the point about which you rotate the lens so that objects at various distance retain their positions relative to each other. So the foreground bush that is below the point of the background mountain stays there when you turn the camera right and left.
We shoot panoramas in portrait so that we get to use the long side of the frame vertically, this gives us the maximum data for the panorama within a set horizontal angle (see above 12 frames instead of 8). Why would you not shoot that orientation, well there are some guidelines for creating visual impact assessments for windfarms and solar panel arrays that specify landscape orientation (but that's a work justification), it could be that the view you want to capture works best with a landscape orientation (its 35° high so would look tiny if you shot it portrait) or there is a bright reflection that appears between 49 and 74 degrees that washes your image out. Ok im struggling to come up with a reason not to shoot portrait unless your head cant and there are a few that only do landscape. Aha, it allows you to use the hotshoe for a bubble level and not have to worry about sag when mounting the camera vertically or for a gps locator (plugs into the hotshoe and needs to be able to see the sky) and not worrying about loss of accuracy.
All the best