I use a BRS 75 gpd 6 stage. I have a sediment block, a 5 micron carbon block, a half micron carbon block, the RO filter followed by 2 DI cartridges.
The sediment block and carbon blocks are cheap. I change them annually and I make over 1000 gallons per year.
My tap water tds is about 140. It comes out of the RO at 2 tds and out of DI at 2 tds.
My water pressure is about 60-65 psi. That is a bit low but things work well. Also, the production is at least 75 gallons per day. I use a 44 gallon Brute trash can for RODI storage. BRS sells a little float switch to turn off the system. It is cheap and simple. It has kept me from having numerous floods.
I think Spectrapure has the best reputation. If you have high tds water, they might be the way to go.