I recommend Logitech's MX Master 3.
Internal battery, with USB-C (and fast charging!)
Bluetooth and USB dongle support
Cross-platform support; Bluetooth works on all systems with support for Bluetooth mice. Optional configuration software is supported on macOS and Windows.
7 buttons, vertical and horizontal scroll wheels; vertical scroll wheel ...
If I understand the question properly you are looking for a USB hub wich connects to the computer through Bluetooh instead of using a cable, am I right?
In that case such a thing does not exists because Bluetooth is a very slow protocol and would not be USB compliant, not only because of the speed but because of the lattency, causing devices to disconnect ...
I was thinking of a USB mouse with a cable that plugs into a USB port, not a wireless mouse with an RF dongle. If I were to use such a mouse, I'd turn Bluetooth off. The question is would a cable-connected USB mouse that got its power via the USB port drain the battery less than a Bluetooth mouse. Thanks.
Each A2DP "service" is Mono-Directional.
A typical device using the A2DP profile for music will not support more than one service (i.e. audio stream), but it's possible. This would need a more complicated chipset so it may not be suitable for the size constraints of "truly wireless" earbuds.
Unfortunately I can't recommend any headphones ...
You could get something like this USB Switch and attach a USB Bluetooth adaptor to it.
It allows you to connect up to 4 USB devices and then it can connect to up to 2 PCs / Laptop with a single USB cable. With the touch of a button you will be able to switch between PCs / Laptop.
Since very few cellphones nowadays have external antennas, and they are not Android but are 2G only, a cellular repeater or femtocell at 20m elevation is recommended.
It must match the cellular voice and data frequency bands used by your provider, wherever you are, and may require regional regulatory approval. They will work, as adding another cellphone (...