Update 8/1/2018:
Thank you for your feedback. We have published a set of drivers and system updates which helps mitigate this issue. This is now available in Windows Update.
We recommend that you install the latest updates to keep your Surface performing its best. You can get updates now by checking Settings > Update & Security > Windows Update.
As a temporary workaround, we suggest that when your Surface is plugged into the power supply, click on the battery icon in the Windows taskbar and set the Power Mode slider to either “Recommended” or “Better performance.”
You can find the details of the latest update on our Surface Book 2 update history page.