Many great suggestions above.
My take of fish, (well, I no longer carry fish in my shop due to limited space) is that no matter how reputable an online fish vendor is, the shipping stress kills.
Most fish if not all, carry bacteria, virus, parasites, just like human, when their immune systems are strong, infections are kept at bay. Once the fish is stressed, the infections take over.
I am not saying QT is useless, it is just scientifically invalid for bacteria and virus infection (for parasites such as ich, your milage is vary). Actually bacteria and virus infections on fish are as common as visible parasite infections such as ich, you just don’t see it. I am very confident on this as I used to work on infectious diseases.
One may say, I follow strict QT protocols and my fish are very healthy. But I have over a hundred fish and most of them are over 10 to 15 years old. Some died from old age. And, I never QT them. I should go grab a beer (or napalm) with PaulB, with social distancing of course.
So the bottom line is, stress kills. No matter how long the vendor QT the fish.
Think about this way, many fish are “QT “ for years in the ocean, and they still have 90% chance to die in the pet trade. Also, the chance of a fish to catch an infection is far lower in the ocean than in a fish tank, because in the ocean, they practice social distancing...
What I am saying here is: go to your local fish stores. Look at the fish before you buy. If the fish look healthy, it may already get over the shipping stress and as long as you provide a good home for it, nutrition wise, tank size wise, and no freaking jerks like a 6 line wrasse, you will have much better success.