Your best bet would be to take the water test report to the nearest plumbing supply house and get their recommendation.
Don't bother with the big box stores, and stay away from Culligan/EcoWater/etc. Those outfits want to hook you for residuals.

I installed a Water-Right softener when we built our new home back in '07. I keep the brine tank stocked with salt and otherwise
never touch the thing. Only issue I've ever had was getting a chunk of bell pipe gasket stuck in the control valve after the
water district did a repair on the main line out at the road. I went to the supply house where I bought it and told em what it was doing.
They sent me home with a new valve and loaned me the tool that's needed for R&R. The old valve wasn't hurt, but I already
had it apart so I installed the new one. Kept the old one for a spare. There's a coin cell battery that keeps the timer running
when the power goes out. That thing has to be replaced once every ten years or so. It's been a very reliable system.