[wanderr]

Under sink RO is not a big deal, you can buy a system for relatively cheap at Sams or probably Costco, and there's not much that you have to know, just change the prefilters when you are supposed to. Depending on the bladder and how much usage the RO system gets, it can take a while to fill a glass, 15-20s maybe? Filling a pot of water is infuriatingly slow.

RO systems waste water as that is how they work, expect your water usage to go up (how much depends on a lot of factors, for us it did not impact our water bill).

Whole house RO systems are probably a non-starter, keeping the water pressure up high enough seems like it would be very expensive.