I dont have a proper QT setup but I have a 33G Long "observation" tank. This is setup with LR, full on filtration and is fully established with some cheap large Kenya trees for the new comers to feel welcomed
I introduce anything new and don't move to the DP until at least 90 days later. Besides observation, it allows me to target feed them and fatten up where they would have definitely been outcompeted in the main tank while stressed by all the activity of more than 2 dozens of fish that they'd have to compete with fresh out of the store.
I do not as I get all my fish from the same local shop. I've had more issues trying to QT/Acclimate new additions vs just plopping them in and letting them settle into their new home asap.
I've also learned the hard way, the evils of not QTing livestock. For my next build, I'll have a QT set up for all fish coming in. For those fish I buy ready QT'd (thru a QT Vendor), I'll watch x14 days. For those not QT'd, they'll go through the 72 day wait. Not gonna take any chances.