Budgie Settings button says "Disable Nighlight mode when windows are full screen." That's the only mention of Night Light in Budgie Settings. I have it disabled because I have redshift app instead.
In regular "settings" in menu, after devices then display, is a manual timer you can set Night Light from. I've never tried it.
Redshift, AFAIK, uses geolocation to determine your longitude/latitude and you can totally tweak the conf. file. (I keep it dim all the time--I credit Kyrios with that old tweak).
I don't know how exactly the built-in Night Light works, but it looks like you can manually adjust it.
Hope someone else chimes in. That's all I got.
