For several years now, we've been using a Clear2o Dirtguard 2-stage system as the initial filtration unit attached to the water supply outlet. If we are going to be at a campsite for more than a day or two, then I will hook up our On-The-Go water softener and conditioner, which, by the way, works great.
Inside for our drinking water and ice, we use an Itehil portable R/O system. It filters out bacteria, viruses, parasites, heavy metals, pesticides, PVCs, PFAS, chlorine, etc. The Clear2o does the heavy lifting, ensuring that any water we use while on "city water" is clean, as well as any that we put into our freshwater storage tank. If we were dry camping and needed additional water from a stream, lake, etc., then the Itehil would make sure that it was safe to use.
Also, I would recommend purchasing a Kactoily 6-in-1 water tester from Amazon. It's the best $50 you will spend on knowing the condition of your water. You can test the water at the source to get a reading. Then test the water coming out from your initial filtration system to get a good idea of what you're dealing with. Distilled water has a reading of 100 (so does water from an R/O system), and source water at campgrounds is usually in the 80s-90s. The water tester will give you a complete breakdown of what is in the water and why it scored the way it did. Again, a great investment for $50.
The Clear2o system costs about a $100, and its ceramic filter can be easily cleaned and back-flushed. The On-The-Go Water Softener costs under $200 and can be recharged with a box of table salt once a year, so it's basically a one-time expense. The Itehil R/O system usually sells for around $250, and the filters only need to be replaced once every year or so.
No matter where we are or what the water's condition is, we never have to worry about having safe, clean water in our rig. And it usually takes me less than 5 minutes to have everything hooked up from the water source to the coach. I'm going to change all my connections this season to quick-disconnect fittings, so that should reduce it to just a couple of minutes max.