I'm not sure what you are trying to ask.............
There are two settings on a digital Varistream which you allude to. If the volume of water is too much for you at the rate rate of 3, then reduce it to 2. You should hear the pump reduce speed. If the Varistream works without pulsing on 3 then you won't have a problem on 2.
Now you want to set the pressure switch side to suit your slower flow.
I would couple up everything including your hose and pole with the tap open. Start the pump and increase the flow to 3 or perhaps 4 for those occassional times when you need a higher flow rate. Get into your pressure setting and decrease it until the pump starts to pulse - stop and go. Slowly up the pressure until the pump runs smoothly. I would then increase it another point or 2 and save that setting. Now you will have no pulsing problems with your preferred flow setting of 2 and you will still have the pressure set right if you need to increase your flow for a first clean etc.
I run my Varistream on 4. I like the flow of 5 for rinsing, but I use more water at this flow rate. My pressure setting is on 3. I have 100 meters of Minibore hose and a Gardiner pole and brush with 2 x 2mm jets. But what works for me may not work for you.
Now BVC has made a point albeit in a rather unconventional way. You may find that working more quickly on each window at a slightly higher flow rate will save water and time. To illustrate; if you need 1.5 litres of water to wash and rinse a window and your pump is pumping water at 1 litre per minute, then you will take 1.5 minutes to wash and rinse that window. If you increase the flow to say 1.5 litres per minute, then the window will take you 1 minute to wash and clean. The higher flow rate will also flush the dirt off quicker where you may find that the slower rate doesn't and you end up using more than 1.5 litres to rinse that window.
Getting the right flow to work rate can save you water and speed up your work rate. But you can also go the other way where you aren't able to clean and rinse fast enough, so you will waste water even although you are quicker.
Water saving is very important, especially if you are using a backpack or trolley.
My son uses a backpack and uses his van mount to fill his backpack up. He finds another way of saving water is to wash the window quickly, switch the water off, scrub and then switch the water back on to rinse. He also advises that the Aqua-adpter on his pole has also helped with water saving.
Spruce