Thanks for the recommendation. Seems like it renders a partially transparent overlay to simulate a lower brightness setting. The notification bar remains unaffected, but I guess it's better than nothing.

Yes. Beware of two things:

1. It can block "Install" button when installing apks from outside of Play Store. Disable it

2. Latest commit is 4 years ago. But I've still chosen it over Red Moon because it's more than 10x smaller (336kB but still very configurable).