I recommend generic mode.
Cropping should only occur on x5 1080p mode. You can switch to 1600×1200 or 1920×1200 to get the full picture (if your display is compatible).
Connecting directly to TV (no switcher) may reduce downtime. In general this is up to the display, some are faster, some are slower. Only way to eliminate it is to use an external scaler with framebuffer.