Performance boost: TensorRT only. Increase performance up to ~5% and lower memory usage in exchange for running a 5-10-minutes optimization pass in a command-line window for _every_ new video resolution. Previous runs are cached. For example, you're opening a 1080p video for the first time, you'll wait 5+ mins. Every other 1080p videos will start instantly, but when the frame size changes due to, for example, black bars cut off, you'll wait another 5+ mins.
With "perf boost" off there's only ONE optimization run for all resolutions below 1440p.