I have a water softener and I love it! We travel out West and encounter a lot of hard water. The soft water stops all the water spots and makes everything much easier to clean. I have a portable unit. The water goes from the faucet through our filters (we have sediment and charcoal filters) to the water softener and into the coach. Everything is external to the coach. We get the filters from the rvwaterfilterstore web site. We have the Flow-Pure 10000. It uses regular table salt for charging.
I st4rongly recommend you get the better brass quick hose connects from the RV water filter store to connect the hoses. They are much better quality than the ones you get from the big box stores.