Hello DevCisse,
Good to see you in Microsoft Community.
If you want to exit the Windows Insider Program, you can click "Leave the Insider Program" below the image and follow the prompts.

Regarding the fresh installation, in theory this will not affect the data of your non-system disk (E drive), but you need to judge your system partition according to the size of the disk during the installation stage, so please be cautious. If you have very important data, you may make additional backups to prevent accidental loss of your data*.*
Step-by-step to make a boot disk in MCT
- Prepare a flash driver with at least 8GB (Pay attention to backup data, because creating a boot disk will erase all data of the flash driver).
- Visit Download Windows 11 (microsoft.com) and click "Download Now" to download MCT (Media Creation Tool).
- Run the MCT, select "Create installation media (USB flash drive, DVD or ISO file) for another PC”, and then choose Language, Version, Architecture (if you are not sure about these, choose "Use the recommended options for this PC"), then select "USB flash drive" in the "Select Media to Use" interface, then make a boot disk.
- Then boot from the USB flash drive and execute the installation program.
And you can visit How to clean install Windows 11 - Microsoft Community & How to perform a clean installation or reinstall of Windows 11 - Microsoft Community****for specific installation steps.
If anything is unclear, please do not hesitate to let me know.
Best Regards,
Mosken_L - MSFT | Microsoft Community Support Specialist