I use two speakers with SL for music during dance shows. The Megaboom speaker works well and it is the computer that it communicates with and any sound from the PC, even SL browsers plays just fine.
My other speaker has a microphone and that was a disaster with SL, it sometimes worked, sometimes didn't, so I deleted the bluetooth connection, again it is just to the DESKTOP computer Bluetooth dongle.
Then I used a male to male 3.5mm cable to the speaker and the PC headphone socket and the sound from SL is just perfect, with good base.
For this reply, I kust used my Headphones on Bluetooth and SL. Yes it works.
Bluetooth works with the PC and repeats anything that the PC plays.
To make a change of output, try Ear Trumpet app, it will re-direct the sound automatically or manuallyand is a free app.
It sits in the app box on the PC by the clock.
The Bluetooth dongle, it is dirt cheap on Amazon (£8 - £11) and supports 6 units, of course one at a time. And far better than a built in one.
Also used it on my Win 10 klaptop, yup it works with three systems on there too.
Hope that helps.