Ok, I ordered the adaptor! Yes, I was suspecting that I will need to disable one of the adaptors. Haven't looked how that is done yet, but I am sure I will figure it out.Unlocking with Apple Watch ("Auto Unlock") requires the support of the 802.11v feature "time of flight" which is only supported by the newer Broadcom Wifi cards, which also support 802.11AC.
The "rub" is that you won't get that feature working with a USB adapter - as these aren't seen by MacOS as native network adapters. You need to have an internal NIC that supports the feature for it to work.
For Continuity / Handoff, you only need wifi that works under Sierra and BT 4.0 - then you use the CAT tool to patch your system.
Oh...and in case it wasn't obvious - disable your internal BT adapter before you plug in the USB one (having two of them running will only cause issues).
You know there is a new feature in Sierra where you can copy something on your mac, and then use paste on you iphone. The same buffer share between the devices. So, will that feature also work after using new BTL and CAT?