Can I use a Macbook (or an iMac) as a Bluetooth Player?
You actually cannot. Let me explain why:


The bluetooth hardware of Macbook and iMac are designed to be "sender" rather than "receiver"...
The software/driver is designed without considering using the computers as bluetooth receivers.


If you must connect two computers in an area where wifi channels are all taken, you can try using 5G wifi connection rather than the 2.4G - and if that still doesn't work, you are out of luck.

Note: wireless audio receivers usually are designed with special hardware component to eliminate lags - and even so there are so significant lags on all devices. So do not expect your computers will sync - in fact, there should be half or one second lag even in an ideal condition.

Hope this help!