How is the task-priority decided?

It would be good to have some idea about how ProjeQtor determines which tasks should be given a higher priority.
IINW there is no help available on this.

My guess is, the priority numbers of the project and the task are multiplied to calculate the overall priority index (= "PI").
Then tasks belonging to different projects can be compared on a single scale.
Regardless of the OI value, the tasks are assigned a resource on first-come-first-served basis.
But if tasks begin on the same day, and if they need the same resource, then the task with a higher PI wins.
Is that the correct understanding?

Case#1: (the default case)
Two projects have Priority = 500. All tasks in each project have Priority = 500.
How are the tasks handled when there is a conflict for a resource?
Is it correct to assume that tasks are assigned the resource in top-down order (but NOT based on their dependency)?

Case#2:
Assume that there are two tasks within a single project, with different priority numbers.
In case of a conflict, how are they assigned the common resource?

Case#3:
Assume that we have two projects with different priorities (say, 500 and 700).
And they have tasks with Priority = 500.
If they have conflict, how will this affect the assignment order?

Case #4:
Assume that we have two projects with different priorities (say, 500 and 700).
And they have tasks with Priority = 600 and 800, respectively.
If they have conflict, how will this affect the assignment order?