Had the same issue on Surface Laptop 3 15". Mouse and headphone would disconnect every five minutes or so. Also the power options in Device Manager where missing so the above options where not working for me.
Went in Setup -> Devices -> Bluetooth Devices and removed all the devices that where linked through Bluetooth. Then reconnected everything again. ~~Have been working without issues for two hours now. Hope this helps anyone else.~~Too soon, still dropping intermittently.