OK, under "Settings", "Update & Security", and "Windows Update" you can control system restarts but not the download and install operations. You can stop automatic downloads if you are on Wi-Fi by setting that connection to "Metered". Windows 10 will then give you a notice when updates are available but will not download/install until you click on the Install button. I believe you can control system updates by editing the System Registry, but I would need to research that
In the "Windows Update" window, click on "Advanced Options". There you should see "Choose how updates are installed". Your choices are "Automatic" or "Notify to schedule restart". It defaults to "Automatic"