Is there a limit to amount of bluetooth devices connected to a MacBook Pro?
Here's the info from Apple site:

Connect multiple Bluetooth devices to one computer
The official Bluetooth specifications say seven is the maximum number of Bluetooth devices that can be connected to your Mac at once.
However, three to four devices is a practical limit, depending on the types of devices used. Some devices require more Bluetooth data, so they're more demanding than other devices. Data-intensive devices might reduce the total number of devices that can be active at the same time.