I use a quick connector but it is to protect the trailer water connector and hose threads from damage caused by cross threading versus the speed to attach the hose.
IMHO one needs to be careful when you test the presure and believe that it is low enough that you don't need the water regulator. You might have run the test when water consumption was high and like CG electricty voltage that can change over time.
In Shelburne on HWY 10 there is a RV Dealer called Gimmi Shelter. I bought mine there when I bought my trailer. They have a well stocked store. I don't remember how much I paid for it.OK now the million dollar question.
Which water regulator is the best to buy, I have to admit I don't use one but after reading this thread I think I will start..