Access the System Services by opening Settings from the Home Screen, tap on Privacy then Location Services, scroll down and select System Services
Apple Pay Merchant Identification This setting is tied to your physical Apple Card. Unless you have a physical Apple Card, there isn't a reason to have this enabled.
Cell Network Search This sends data to Apple to let Apple know which cell towers are being used. It's safe to turn this off.
Compass Calibration This is specifically for the compass app. If you use Google or Apple Maps, I recommend keeping this on.
Emergency Calls & SOS Keep this enabled.
Find My iPhone Keep this enabled incase you lose your iPhone!
HomeKit If you don't use HomeKit, you can freely disable this.