One for one or 50% efficiency is about as good as it gets for 99%+ removal in home systems. There are some powered systems that claim 66% but the ones I've seen are ~ 96% removal and require stupid expensive proprietary filters. Pentair GRO based systems are what you want to look for. https://www.amazon.com/Reverse-Osmosis-System-Recovery-California/dp/B071SB26BV for an example. I hade a black&white 50/50 built for me by https://www.purewaterproducts.com/black-and-white-ro

Hmm. Where to start. First, literally no one but the people selling remineralizers and/or alkaline filters recommend them. While not proprietary, they are expensive and completely unnecessary no matter what they try to scare you with. I'm assuming you're in a first world country with ample access to food -you'll be just fine. I personally like and recommend a Pentair GRO encapsulated membrane for water saving reasons and that's always a good thing with wells. It is proprietary and more expensive than a standard membrane but with my high dollar water, it pays for itself easily. https://www.purewaterproducts.com/black-and-white-ro I recommend talking to these people with any questions. https://www.amazon.com/Reverse-Osmosis-System-Recovery-California/dp/B071SB26BV this is an equivalent system on Amazon although it doesn't come with a tank or faucet which the PWP one does and you get a very nice faucet, tank, and all the required plumbing and people that actually answer the phone and emails.