Dithering from 48K 24bit iZotope

dithering means to reduce the word length by introducing a low level noise to a signal...

the most common is from 24bit to 16bit.

src is something entirely different.
 
You'll only have to dither for 16 bit if you're rendering your tracks directly to a .wav file that's going to be burned to CD. And only if you're resampling from 48 to 44.1. In-project, it won't make a difference.