OS is unresponsive or lags - Remote Procedure Call high CPU usage

[Jay_TO]

Made the jump to Win10 today and not having a good time of it. After 6-7 failed attempts to install with the Windows Update path, I gave up and went the ISO DVD route. It completed without any major issues however now the system is a dog. Start button will work sometimes. Launching Settings will work sometimes. Updates hang forever then produce a 'Failed' message. The OS seems preoccupied with something and when I review the Task Manager, the Service Host: Remote Procedure Call process is steady at 27-28%. Is this what's killing the responsiveness of W10 and if so, what is it trying to do?

I'm open to suggestions... this is no longer fun.