RO systems are not practical for whole house in the RV...RO is usually used for single drinking water tap only....recovery of cleaned water will not keep up with shower and general demands in an RV. I am probably going to go with a two or three stage system which is pretty much what you are talking about. Depending on your unit and demands location is custom and specific to each situation.

I can only speak for myself but, it may also apply here.  I contacted the RV Water Filter Store explaining my setup and common RVing situations.  Richard Dahl responded quite rapidly with his suggestions for a system.  I, for one, really appreciate the intimate customer service and prompt response.

Ultimately I ordered a "Dual Jumbo SED5 & KDF-GACBB" that sits in a transit box under one of my slide-outs to keep it out of the sun.  The high flow filters are great and do not impede the water flow to the rig.   The filters I ordered are able to be cleaned and should last a long, long time.  (I also "deleted" the internal filter on my rig and run with the filter canister "empty".)

I have "stainless quick connects" on everything (and ordered some custom "short" hoses from them, too) making setup very rapid and provides the ability store everything in the same container in my basement when mobile or Boondocking.   My system goes from a "Watts X65B" to the jumbo filters, to an "On The Go" water softener, to the fresh water inlet.  When I prep for Boondocking, I use the same setup to fill the fresh water tank.

For times when I am out in the boonies for an extended stay, I augment the system with two five-gallon water jugs that I bought from Wally World filled using the same setup.

Hope this helps.  It works for me.

 

 

Echoing the praise for RV Filter Water Store... our supplier as well. We have a dual canister system from them that is hooked up at the water intake that everything goes through. And then we also have New Wave 10-stage single canister drinking water filter undercounter.