Shield Studies are in the "Privacy & Security" settings:
"Allow Firefox to install and run studies"
"Follow On Search" is AFAIK controlled by the Telemetry settings in the same dialog in "Privacy & Security".
ignore one's updating preferences
Are you sure? They're add-ons, so they should follow the add-on update preferences. Given that aushelper apparently does nothing aside from modify the update URL to include info whether the system is affected by some bug, it's hard to see how it wouldn't respect the settings.
"Follow On Search" is AFAIK controlled by the Telemetry settings in the same dialog in "Privacy & Security".
ignore one's updating preferences
Are you sure? They're add-ons, so they should follow the add-on update preferences. Given that aushelper apparently does nothing aside from modify the update URL to include info whether the system is affected by some bug, it's hard to see how it wouldn't respect the settings.