How to Handle Severe Lag and Heat After iOS Update?

I've been using an iPhone 16 Plus and recently upgraded to iOS 26 about a month ago. Since the update, I've been facing major performance issues—I'm experiencing significant lag when switching between apps and gaming, and the phone tends to heat up a lot. I understand that updates can take time to settle, but this feels excessive after a month. I reached out to Apple Support and they provided a few options:

1. Restore from a previous backup to revert to an older iOS, but I'm unsure which backup was for the older version.
2. Request a one-to-one exchange for a device running iOS 18, but this also involves the same backup and data restoration challenge.
3. Request an exchange hoping the new device won't have the same issues, but I'd still need to restore my data.

I'm curious about whether manual data porting is a feasible solution when transferring from a device on the newer iOS to a new one on an older iOS. I'd love to get some advice on what to do regarding these options! Is manual data porting realistic for a downgrade?