Avoid culligan. Im a mechanical contractor so i got a deal on their gold equipment. Ive replaced alot of parts in 5 years. Go with fleck. Backwash can go into indirect drain into septic or sewer but not into storm drains. Best solution for dischsarge is to dump in a drywell (dig a hole lay down landscape fabric and fill hole with stone wrap the fabric around it and run a piece of pvc out of it and backfill. It will allow the water to perculate into the ground.
I have the following in order. ground is high in iron and had a little bit of bacteria.
neutralizer
softener
coarse sediment filter
greensand filter
fine sediment filter
UV
RO for drinking water only
The water is completely tasteless after all that. Costs about 650 a year in sal/filters/uv bulb. Filtration causes pressure loss and ph drop. Run system at 70pounds but more like 40 after all that. PH starts 7.1 but gets down to 6.0 or a little below after RO. Public water is accross the street but our town will not allow it