The importance of water quality IN QT as an ich preventative.
I'm personally not a fan of medicating in qt in the absence of visible symptoms. The species I keep (smaller species like gobies, blennies, and damsels, basslets, etc) influences this decision: no thin-skinned critters like angels and tangs. So your mileage may vary. Take that into account. Angels, tangs and rabbits are very vulnerable.

However, I am fanatic about water quality 24/7 for new fish. Keeping alk around...

About skimmers: y/n/maybe? FYI And they aren't your swimming pool skimmer...
A skimmer produces skimmate, a brownish watery to dark murky yuck that otherwise is dissolved in your water. It does this by frothing the water, and the more efficient skimmers churn the water into a foam that would stand like meringue in a cup. Do you want this stuff gone? Well, lps and soft coral will consume a bit of it. But unless you have a packed reef, their usage can't compete with a skimmer. And, catch-22,...