I wanted to unlock my bootl oader so that I can root the device for performance and battery improvement.when I try to turn on OEM unlocking, I am told that the step would deactivate device protection features. I want root and device protection .I dont want to flash custom ROMS or recovery .I just want to root the device and turn the switch back off. Is that possible?
It appears my comment was incorrect, once you Enable OEM Unlocking in developer options, you have disabled Factory Reset Protection completely.
If you have Developer options turned on, you can also turn off device protection from your device's Settings app. Tap Developer options and then OEM Unlocking. - Source
And no, once you have unlocked the bootloader (required to root) you can not re-enable this switch, it is greyed out and non-functional, unless you relock the bootloader which cannot be done without have a completely stock image installed, meaning no root, custom recovery, or other modifications to the device.