How to Downgrade to Android Nougat
If you make the move to Android O Nougat you aren't stuck. You can downgrade to Android Nougat if your device starts to struggle.
If you get tired of the bugs you can get off the Nexus 5X's Android O beta update at any time. You simply need to unenroll your Nexus 5X from the beta program.
To do that, head back to the Google Android beta page and click the big green button that says "Unenroll Device."
Soon after that, your device will be sent an OTA update that will wipe all user data and install the latest stable public version of Android. As of right now, that's the May Android Nougat build.
This will wipe all of your data so make sure you backup all of your data before you unenroll from the program and install Nougat.