I installed a water filter system in our Montana about two years ago. I used the equipment listed below. Filters have 3/4" inlet and outlets. Used 3/4" Pex pipe and have little to no pressure loss. System is very effective. Even works on water in the Yuma AZ area, some of the worst water quality I have run across. NOT the cheapest, but it work. We do not buy bottled water anymore.
https://www.rvwaterfilterstore.com/j...-filter-system
https://www.rvwaterfilterstore.com/u...-filter-system
https://www.rvwaterfilterstore.com/o...water-softener