bluetoothmacbook pro
I'm using a bluetooth earphone very often. It works really well with iphone and ipad, but it just doesn't work well with macbook pro retina 15". The range and connectivity are pretty bad.
I'm thinking about buying an external bleutooth adapter. Can I use it?
You can't run Bootcamp from an external hard drive, but you can install Windows via a virtual machine (MV Ware or Parallels are the best known). If you install Windows on the internal drive you have the option of booting from it directly or using one of the VM machines while running Mac OS.
As for the hard drive size you should consider the 768GB drive if possible. The drive space goes quickly and isn't upgradable. (Well, it is, but AFAIK nobody makes larger or faster replacement drives.)
The OSs run independently of each other, so you don't have to worry about cross-contamination. When running BootCamp you can't even see the Macintosh partition.
In my experience it works as well as can be expected considering the limitations of running software on hardware that wasn't specifically designed for it.
Good Luck.
Update: There are now several competitors, such as Luna Display, as well as native support in iPadOS 13 + macOS Catalina, called Sidecar.
The app Duet Display lets iOS devices connect to a Mac that is running at least OS 10.9. The Mac needs duet software which is a free download and connects via Lightning port to the Mac in question to send the video.
The Mac app is a free download and the iOS app is available for purchase on the iOS App Store.
Best Answer
Yes, as @Buscar웃SD said, you can use an external Bluetooth adapter. On my Macbook Pro 13" I had to use Apple's Bluetooth Explorer to set my USB adapter as the active controller. This page describes how to download and use Bluetooth Explorer.