[8-Ball]

The way I see it is as follows.

Flow rate through a restriction is a function of the pressure drop across the restriction.

Given a number of restrictions between the outlet and inlet of a loop, the total pressure drop is additive.

As an example, at a given flow rate, the pressure drop across the cpu block may be x, y for a gpu block, and z for all of the tubing.

Thus, to maintain this flow rate, you need a pump capable of providing head equal to x + y + z at the given flow rate.

Beyond that, the order of the components does not matter, as the pressure drop across a given component will always be the same for a given flow rate.

Is that correct or not.

In other words, if you have pressure x at the block inlet and pressure x-dp at the outlet, would the resulting flow through the block be any different if the pressure was x+dp at the inlet and x at the outlet. The pressure drop is still dp, so it shouldn't matter.

If the flow rate through a block is the same in these two scenarios, then given that the geometry doesn't change, the velocity of coolant shouldn't change either.

8-ball