My understanding with the all valve is just before the pump's shutoff tee, there is a line that goes to the all valve, and another line that goes from the valve to the pipe that feeds the pumps. The specific setup may be different between rage and waterman pump.
Any fuel not going to the all valve goes to the tee, which is what the higher handle on the left of the cockpit is controlling. You may hear "trim the fuel" or "trim the pumps". Thats what they are talking about, moving that handle anywhere from almost fully closed to almost fully open to get what the crew chief wants. "High side" is having it fully open, fully closed turns the engine off. It works by porting fuel to the barrel valve or to another line that goes to the pipe that feeds the pumps.
Past the tees, both pumps have a line sending fuel to the barrel valve. Both enter the front of it. The barrel valve opens and closes with the throttle blades. It also has three other lines. One that sends fuel to the engine, and two returns for excess fuel. Those lines go to a wye with check valves. The wye's outlet is another line that goes to the pipe that feeds the pumps. The barrel valve is controlling how much fuel goes to either the one line going to the engine or the two return lines going to the wye. At idle, most of the fuel is ported to the barrel valve's return lines. At full throttle, most is going to the engine.
That one output line from the barrel valve goes to th flow meter and all to the engine. There are no other paths for fuel other than to the engine once it enters that output line. Pass the flowmeter, it goes to distribution block(s). Different teams do it differently. The premise is the same though. The fuel has to go 4 places. To the supercharger, to the intake manifold, to the left head, and to the right head. Some teams have one distribution block feeding one or more main distribution blocks. Some use wyes and distro blocks. Of course, each head has jump tubes that come off the head's main pipe that lead to a nozzle, the distro block(s) will also have lines that lead to a nozzle. Each nozzle will have a jet, same as like a nitrous jet. Some nozzles will have check valves that will not flow fuel until a certain pressure is reached.
Much of this I learned from Nikolas with Darkside Racing up in Canada, either from his YouTube channel or the team's website. If you want, I can look for links.