Overall Verdict: ⭐⭐⭐⭐ (4/5) – Essential for some, irrelevant for most. What Is It? "Disable full-screen optimization" is a compatibility setting in Windows 10 and 11. When you run a game or app in exclusive full-screen mode, Windows 10/11 by default actually runs it in a hybrid "borderless windowed" mode via a feature called the Full-Screen Optimization (FSO) . This is meant to make alt-tabbing faster and overlays (like Xbox Game Bar) smoother.
You frequently alt-tab, use overlays, or play modern DX12/Vulkan games (they handle FSO well).
