Yes, the storage size has gone up considerably. You can transfer your data from the iPhone 8 to iPhone 14 once you turn on the new device. Make sure to enable the Bluetooth connection on both phones to start the process. https://support.apple.com/en-ca/HT210216

I don't think you understand the issue. nothing to do with iphone transfers.
Under iphone storage the last category is system storage. 
after hours of troubleshooting .. it seems background app refresh needs to be disabled or it leaks storage space.

This page might help https://appleinsider.com/articles/22/05/29/how-to-fix-system-data-filling-your-iphones-storage

It seems the issue was from an issue with iOS. As it was a brand new iPhone, have you tried to contact Apple support and ask them? They might have better diagnostic tool to find out what happened.https://www.apple.com/ca/contact/