Question about Logitech M720 Triathlon

Yes that should work You just can't use Logitech Flow features

Since the driver software for the mouse including Flow took up a whopping 240MB and can't do much more than the (also not very useful) Setpoint, I cleaned all the Logi bloatware off the computer again and then put the mouse (or the MYX Ergo) into operation with the normal MS driver. It works perfectly - but as Totoro says, I have to do without Flow and useless gimmicks. Instead of Flow, I use InputDirector - old, useful and small footprint.
It's like before: Logi makes bad software. In the past, the hardware was always excellent. Today that is no longer always the case. As Borel said: "Logitech lost its soul in the IPO".

Yes, this works per device, a Unyfying adapter is simply required (or Win 10 with Bluetooth Smart).

Attention! You can only establish a connection to the mouse with Bluetooth from Windows 8 or higher. Since you only have a Unifying receiver for USB, you must pair the second PC with Bluetooth. I tried it with Windows 7 and it really didn't work. I think it says so on the website. Or you can use 2 USB receivers as already suggested. But I have no experience with that