I can't help much with any of your questions, I bought my RO and have no desire to build one. I think you need to include a little more info. How many taps now and in the future and will you have vacuum? How much sap per day on a good run do you expect and how fast do you want to process it? That will help determine how big of an RO you will need and what it may cost.
First introduced to making maple syrup in 1969
Making syrup every year since 1979
3 x 10 oil fired
Revolution syrup and max flue pan
Almost 1300 taps total with 900 on high vacuum
Bought first Marcland drawoff in 1997, still going strong.