Im cutting an interview which uses a lot of B Roll. If my interview footage is on layer 1 (graded and noise reduced) and my B Roll is on layer 2 (graded), will Premiere process the parts of layer 1 that are being covered up by my B Roll? The noise reduction is quite render intensive.
I've always found that Premiere seems to read what is on the hidden layers and if you have noise reduction, blurs, heavy third party plugins, etc. it can slow down the render process. Even though it really shouldn't. So when I have layers like you described and render times need to be fast, I will trim back the hidden video layers to their points of transition or cut. It does make a difference.