I run a water filtration business. We supply several hundred local businesses and maintain an online store. It's very interesting to read these posts. I want to toss my 2 cents into the conversation.
First about RO: RO is high waste and really unnecessary for filtering potable water. I would recommend it for non potable water because of it's ability to remove tiny viruses and such. (there are better methods)
Why did I decide to switch? I began finding large amounts of bioslime growing in reservoirs. I switched to UF and the reservoirs are always sparkling clean at service intervals.
If you have RO, it is very important to change the carbon pre-filter frequently. The chlorine in municipal water will damage RO membranes and the carbon pre-filter is the mechanism for removal.
Whole house canister filters are not very efficient for the RVer, too large and not very effective without at least 4 separate processes.
If minimizing filtration, use a sediment 5mic and activated carbon. This is the biggest bang. If you wish to go further, add a membrane to remove tiny particles (I like UF) and finish with a carbon block for taste and odor. The water will be clean and taste great.
We sell a compact 4 filter system $200***Link Removed***, easy to install and replacement filter set is only $49 annually.
My daughter created a set up for a vacation house. Same system as above that attaches to a hose and has a built in faucet....clever for filtering from hose bib and totally portable.