Use a shortcut while at the PC, USB when you can take a device with you, Bluetooth when a personal device leaves with you, and a gesture when you remain in view but cannot use your hands.
Prefer a shortcut when the keyboard is within reach. A gesture is useful when your hands are occupied or the keyboard is farther away while you remain in camera view. Practice both before relying on them.
It suits people who use one designated USB device as a physical trigger: take it when leaving to run the selected protection. It does not encrypt files on that USB device, and removing an arbitrary USB device does not trigger protection.
Choose a stable device that actually leaves with you, allow time for brief connection drops, and start with a reversible action such as Windows lock. Do not let occasionally sleeping headphones directly restart or shut down the PC.
A gesture is an explicit command while you are in view. Away detection acts after continued absence and helps when you forget, but it needs more conservative timing.