The partially irresponsive backlight settings should be fixed in the latest nightly update and will be pushed to stable later this week. If you're running in the stable build, refreshing should work as a workaround.
As for loading times, backlight should not impact the performance too much (based on our experience, but we haven't done any specific test regarding that). Outline, though, seems to impact performance massively. If outline is switched on, we recommend to disable it while editing and maybe turning it on again before exporting if it's needed.
Thank you very much for your feedback!