I have recently been using Linux Mint 19.3 Cinnamon on my old desktop at home (purely for some lab stuff). Upon initial setup, I connected my Bluetooth Keyboard (Logitech K380) and Mouse (Logitech M720 Triathlon).
Keyboard was working great with no faults/delays, but mouse was ridiculously slow. I tried the mouse sensitivity in the GUI to no avail. My old Bluetooth mouse was working fine.
After some digging around online, I come across the following fix:
# echo 0 > /sys/kernel/debug/bluetooth/hci0/conn_latency # echo 6 > /sys/kernel/debug/bluetooth/hci0/conn_min_interval # echo 7 > /sys/kernel/debug/bluetooth/hci0/conn_max_interval
Then unpaired and paired my mouse. All working fine now!