well pressure tank / external spigot
I'm thinking that the pump handle must be on a different line, after the pressure tank.…if the pump handle was plumbed directly on a T from the well line and before the pressure tank, there's no way for the pump to get activated to supply pressure to the pump handle

That reasoning is erroneous.
The pressure for the system is pretty much the same throughout, not counting friction losses while the water is moving and other tiny effects like that. If you open a valve anywhere in the system, the pressure for the entire system drops. It doesn't matter where the valve is.

Anyone know how these are generally plumbed before I dig it out and take a look?

There's not really any &quot;generally plumbed&quot;, other than most installers will follow the path of least resistance. There's not any good reason that there should be a separate line from the pressure tank back to the spigot, so by far the most likely configuration is that there's a water line from the well to the spigot, and then from there to the pressure tank and the rest of the system.
One possible exception might be if there is a check-valve between the spigot and the pressure tank.
In many jurisdictions irrigation lines are required to be isolated from the household/potable water supply using a double-check-valve to ensure that no contaminated water can go backwards from the irrigation line into the potable line. But note that that sort of check-valve prevents backflow from the spigot, not backflow from the pressure tank. Only the latter type of check-valve would interfere with the operation of the spigot and require a separate line back to the spigot and there's no good reason to install one like that.
The usual double-check-valve configuration wouldn't pose any problem at all with respect to the pressure switch for the well.
Another possible exception might be if there is a water treatment system (e.g. filter, softener, etc.) present and there was a desire for the water from the spigot to be treated. In that case, a line would have to return to the spigot from the output site of the treatment.
I don't think these kinds of exceptions are likely. But of course there's no way to rule them out completely.
There remains the question of why you want to know how the lines are plumbed. Presumably you have some other broader goal in mind that you are trying to solve. Without knowing what that goal is, it's impossible to help with it. Consider posting a new question where you explain that goal, describe what you've done so far to solve it, and what specifically you need help with.