I wish you luck! You should read some of the reviews on that type pump. They are made to be easy to install and replace, because you will need to replace them often. You don't hear about Cycle Stop Valves in your area because the ones we installed 28 years ago are still working, as well as the pumps they were installed on. For that reason many people who sell pumps for a living try not to let anyone know about Cycle Stop Valves.
Getting 86 PSI from a regular submersible or jet pump has nothing to do with the efficiency. A 10 GPM, 1/2HP submersible can only build about 90 PSI max, so you don't want to work it at 86 PSI. But a 10 GPM, 1HP submersible can do about 180 PSI max, and would have no problem operating at 86 PSI or even higher if needed. Even a multi-stage jet or booster pump would work. The CSV1A is adjustable from 15 to 150 PSI, and could easily be set at 86 PSI using a small 20 gallon size pressure tank and a standard 70/90 or 75/95 pressure switch setting.
The CSV is a simple mechanical valve with a single bolt to adjust the constant pressure desired. It works with the old reliable pressure tank and pressure switch method and doesn't require a very large pressure tank. The CSV would work with a normal submersible, jet, or multi-stage booster. You could use the CSV as in the PK1A kit to control a standard jet pump, and boost the pressure from the well pump the same way you are doing with the Scala. You could also just increase the size of the well pump and use the CSV to control the one pump to deliver the 86 PSI you want. Increasing the size of the well pump would be best as it is still a one pump system that way, which is less complicated, expensive, and more reliable than a two pump system. But even a two pump system can be very reliable when both the well pump and booster pump are controlled by a CSV.
A constant 86 PSI pressure is good as the homeowners are happy. But that will make them miss it that much more and that much quicker when the variable speed pump quits all to soon and when least expected and least convenient. Constant pressure is great. But a simple, mechanical way of getting constant pressure like a Cycle Stop Valve, is much more reliable than a variable speed type pump.