Series is good. You can also plumb the saddle tanks to drain into the front tank. I would choose series because it simplifies the tubing. The last tank in series has to vent to the outside of the jet. I like to make the vent accessible so I can hook up my jersey modeler to catch the overflow
In the tanks, use BVM in tank tubing (cut it 3/4” shorter as it expands in the tank) but it stays pliable for the life of the jet. Use large or extra large Tygon for the rest.
You will only need 6mm from the front of the UAT to your pump. Your turbine will be fine with a medium sized UAT. Once you get to 180N+ turbines will it become critical to use large fittings.
I like barbed fittings on the suction side secured with safety wire. Many people use festo on the suction side, so it probable doesn’t matter. It helps me sleep better at night though!