So, I just learned that the Reverse Osmosis system uses an "air gap" faucet, which the manufacturer said, means I need to use the provided faucet, not connect another faucet like the ones above. So it looks like I may be drilling that hole afterall.
Drilling that hole, particularly in "quartz" (which is a synthetic material) is no big deal. You could buy the diamond or carbide bit to do the drilling yourself if need be.
I have well water, and even after a chemical free iron filter, the water isn't drinkable in my opinion. So, I installed an RO system under the sink. Not only that, but I have a soap dispenser and an air switch for the disposal, so the installer drilled FOUR holes on site. No big deal. He did this in minutes.
You just need to ensure that the RO faucet is deep enough to penetrate the thickness of the countertop, and that you install it in a location not to interfere with anything else there, like the back of the sink.
There's very little pressure from an RO system, so a dual input faucet would make no sense anyway. The undersink RO systems have, generally, a 1 gallon pressure tank, The first 10-12 ounces come out readily, then it peters out to next to nothing as the pressure tank drains. If you think, for example, that you'll be filling the pasta pot to boil water from your RO system, an undersink unit won't work for you, you'll need a larger system. It's basically for drinking water, however I have a "Tee" in mine and I feed my refrigerator's icemaker, too.
The photo shows the work in progress last January. The wood frame is to hold the farmhouse sink. The hot and cold water is in, as is the drain in the right corner of the sink base. The disposal is there. The astute will note the hole in the upper right of the cabinet; that is for the loop for the dishwasher drain...
Now, in my car wash days, I had a
3000 gallon per hour RO system, with a massive multistage pump, membrane and filters that were the size of Sidewinder missles. No, you don't want that...
