For reasons, listed below but not needed to answer the question, I have to export a ProRes 422 1080i 29.97 file to exactly the same specs in media encoder. Does the 8 bpc vs 16 bpc vs render at maximum bit depth have any effect on the image?
We combine our audio mix and Graded master in FCP 7 and export reference quicktimes to episode engine. The files coming out of Resolve 12.5, even though they match our sequence settings and our export settings, are being re-encoded. This cause our export time and file size to match a self-contained export.
My understanding of the 16-bit and Max Bit Depth settings is that some of the effects in Premiere use 16-bit, and therefore if you enable the Max Bit Depth rendering at export, you would get the full benefit of those 16-bit effects in improved color fidelity. For myself, editing with formats that are only 8-bit anyway, I don't bother. Higher bit-depth formats like ProRes at 10-bit would benefit more.
That said, I don't believe you are rendering any color effects from Premiere - you are simply "transcoding" the existing ProRes file to a new ProRes file. Is that right? If so, then I don't think it's going to make any difference in that case. But I'm not betting any money on this. I am happy to be corrected if someone knows better!