How can I completely disable Aero Peek?

I don't know if this completely disables Aero Peek but you can try this:

1. Right click on the taskbar and go to Properties.
2. Clear the checkbox for: Use Aero Peek to preview the desktop
3. Search for "Adjust performance and appearance in Windows" with the Start Menu
4. Uncheck the boxes that have to do with Aero Peek or Aero (or just check Adjust for best performance which should completely remove any elements of Aero in Windows)

Additionally: in Personalization, are you using the basic theme instead of the Normal Windows 10 theme? Try disabling the Theme service completely and in the "Adjust appearance and performance of Windows".

Here's how to disable Aero Peek:

1. Right-click the Start button.
2. Select System.
3. Select Advanced system settings on the left side of the window.
4. Under the Advanced tab and Performance section, select Settings….
5. Under the Visual Effects tab, make sure that Enable Aero Peek is unchecked. You may need to select Custom: before.
6. Select OK or Apply to confirm your settings.