neatly summarised in one image
A few gems: "Real-time protection: This helps find and stop malware from installing or running on your PC. You can turn this off temporarily, but if it's off for a while we'll turn it back on automatically." (emphasis mine)
"The BitLocker recovery key for your device is automatically backed up online in your Microsoft OneDrive account."
"Microsoft doesn't need to ask for access to your Skype and Outlook.com contacts because these other services are both owned by Microsoft and tied to your Microsoft account."