Hello, Louis Gosnold-Jones
Welcome to Microsoft Community.
WinToys might have initially given you access to the Ultimate Performance plan by tweaking system settings or registry entries. Now, it says your device isn't supported, likely because Windows updates have changed compatibility or functionality. These updates might have altered how power plans are managed or detected. Also, since you've upgraded your laptop's hardware (like adding a new SSD, extra RAM, and repasting), these changes might affect the system's power management settings.
I suggest removing the SSD and extra RAM, and rolling back to an older version of Windows to see if that helps. If there's no rollback option, you can download an older version of Windows from sites like rufus.ie or uupdump.net and install it using a USB drive. Just make sure to back up your important files first.
Other third-party apps (like Lenovo Vantage, Lenovo Legion Toolkit, or Process Lasso) might also conflict with WinToys, causing it to misinterpret your device's compatibility. You could try a clean boot. In a clean boot state, the system only loads basic drivers and startup programs, minimizing interference. This can help determine if third-party software or services are causing the issue. If the problem goes away in a clean boot, it likely means a third-party program is the culprit. You can then gradually enable the disabled services and startup items to pinpoint the exact software causing the problem. These steps might seem a bit complex at first glance, but make sure to follow the instructions step by step to avoid unnecessary trouble: How to perform a clean boot in Windows - Microsoft Support
Yuhao L
Microsoft Community Technical Support