FYI, QuickCharge or not, you're never going to get the full charging speed from a USB-A adapter. The reason for this is that USB-C to USB-C devices communicate their power requirements and capabilities before charging starts. Since a USB-A charger cannot do this, the cable is required to have a resistor in it to identify the maximum power.... and based on the USB-C specification, that maximum power from a USB-A charger is 1.5A. There's also a ton of USB-A to USB-C cable makers who are improperly designing their cables without that resistor, which means you run the risk of damaging the charger or phone with an out-of-spec cable. Check out some of Benson Leung (a Google engineer who has been testing a ton of cables)'s reviews for more on that.
If you want the full 3A charging speed that the 950/950XL is capable of, you'll need a native USB-C charger. The only one I've seen that meets the OP's requirement for a removable cable is the Google Dual-Port USB-C charger:
https://forums.windowscentral.com/e.../store.google.com/us/?hl=en-US&token=axbs15dd . This Google charger is capable of 4.5A of combined output (up to a max of 3A per port). If you have two devices connected, I believe the idea is that the device that needs power more gets prioritized. However, one thing to keep in mind is that despite the Google charger and the Microsoft charger both being capable of 3A, for some reason the Google charger is not properly working to power the Display Dock (if that matters at all to you).