I have a 6s, 16GB. I’ve tested iOS 11 since it’s release at WWDC and I’ve had all the log files clog this device up, but I still didn’t have any issues with stuttering and opening apps after the second beta. I did a clean install of the production release and performance is great.
Doing a clean install and setting up as a new device is a pain but it will help you clean out your device, especially if you always do OTA updates. And yes, backups get corrupted. Restore and set up as a new iPhone. Don’t be lazy.