So, after multiple reboots, and accepting software firewall notifications, it seems to have settled down, a bit.
As far as networking goes, i have a full unifi setup (Security Gateway, Switches & AP's) ... as mentioned, when using MSFT Mouse Without Borders, i didnt have any issues.
PC is a AMD Threadripper 1950X (16 cores, 32 threads) 64GB ram.. and no CPU issues at all.
Laptop is a Razer Blade 2019 Advanced - Intel 8750H, 16GB ram.... also nothing hitting CPU
I can only assume that it took a while for the Multiplicity protocol to worm through my network, both over WiFi and LAN.
Weord though, as MWB worked first time... 
Thanks again for the help guys! 