Let me try this. What you need looking top down are equal opposing angles at each side and generally something between 2 and 3 degrees will be okay. Less is much better. If you get past 3 I think I'd start to be concerned as I don't expect it will work smoothly for you. Looking at the side view, you need opposing angles at each end but you'll generally need an extra 1 degree (or maybe a bit less) to compensate for spring wrap-up. A lot of the stuff on the internet falls into two categories: YouTube videos which I don't pay any attention to. These can be awfully bad, actually. And non-video stuff written for either dragsters or off-road vehicles (which you don't have and which will have notably different considerations).
As for left to right offset and up/down offset taking care of themselves as I said hopefully but there can be complications. If you could see the driven u-joint going through the operating angle (assuming you have an angle and that the u-joint isn't running straight with no angle), you would see it travels in an elipse...which will have 4 quadrants. The driven joint will be accelerating and the receiving joint will be more or less decelerating at the same speed. And when that happens you have a nice smooth transfer of power. If it doesn't work that way you will have one joint arguing with the other and then you'll have noise, vibration, etc and the u-joints will wear out. In my experience it does not take much to mess things up. An up/down (side view if you prefer) coupled with allowance for spring wrap-up will usually produce at least for a while a compound angle and for that you need to figure out the operating angle for each of the u-joints. They'll be different. I've seen some offset situations where the spring wrap-up was just omitted, but you know all that does is to transfer that angle to the top side (if you follow that explanation). Point being if your rear end (and this is really a given with the setup in the AD truck) wraps around under torque, it will flex the springs and allow the pinion angle to change...if your bed is off and you're a passenger you can easily see this happening as the truck is driven. You want that 1 degree allowance to bring the pinion angle into agreement with the angle of the u-joint at the other end (at the transmission). When that happens, things will be Jake. But you will have a compound angle there...either by virtue of having added a degree more offset or by allowing your drivetrain to add a different one for you. And during travel you won't always be applying enough torque to try to wrap your rear end as much.
