If you move your iPhone 7 or iPhone 7 Plus to iOS 13.4, and you can't stand its performance, note that you can no longer downgrade to the previous version of iOS 13.
Apple has stopped signing on iOS 13.3.1 which means you can no longer use a loophole to drop back in an effort to improve your phone's performance.
If your phone is really struggling on iOS 13.4 you might consider moving to Apple's beta software. It has the potential to improve your device's performance.
If you're unfamiliar with the iOS 13 downgrade process, take a look at our guide.