You Can't Downgrade to iOS 10.3.2
If you can't stand the iPhone 7 iOS 10.3.3 update's performance you're on your own. Apple's closed up the iOS 10.3.2 downgrade path.
Apple is no longer signing off on the iPhone 7's iOS 10.3.2 update which means you can't downgrade in an effort to improve your device's performance. You can't downgrade to anything older than iOS 10.3.2 either.
This is a permanent change and it means you're stuck with iOS 10.3.3 until Apple rolls out the iOS 11 update. You can try the iOS 11 beta but it's plagued with numerous issues and isn't a good alternative to iOS 10.3.3.
If you're unfamiliar with how the downgrade process works on the iPhone 7, take a look at our detailed walkthrough.