It's a long time since I used Windows but I can't think of any reason why it would not be suitable for dealing with two audio channels. Consider Audacity
You still have not told us what quality of audio you are dealing with.
Technically I don't want to have several speakers for a laptop, a desktop, and a cell phone.
So, I just want to integrate all sound for one earphones. (it might be minimalism. ;p)
Furthermore, I dont know what kinds of quality sounds I can choose.
To return, I usually spend most of my time in front of my monitor, so I connect my bluetooth earphones with the desktop most of the time. However, sometimes I need to check my cellphone such as instagram, facebook, and msgs. At the moment I need to connect my bluetooth earphones with my cellphone after disconnecting my desktop to hear sound. This is really tiring to me.
So, I just want the quality of sound when I connect my earphones with my desktop or cellphone directly.
For the reason, I would like to integrate two sound streams first, and send to my earphones.
Is the streams of two sound source too heavy to be handled by RasberryPi?
p.s. I cannot connect my iphone with windows10 through bluetooth.
I think there is a problem of compability. So, anyway I need to make one seperated device totally to
access my iphone and deskop at the same time. The device will be used only for sound streams.