There's a lot of things to take into account on the subject.
I do believe it lowers igf even if you're taking exogenous gh. That's my belief and finding.
Now Meadows. First off, he's a mutant. None of us are lol so there's that. His igf could be 5 and he'd probably still be a freak.
Also, John is very health conscious and this plays into him using nolva due to the negative effects on cholesterol from certain AI's.
Also, if you don't aromitase much, which I think I've heard him state on a podcast he doesn't, there's really no better alternative then nolva IF, you have pre existing gyno since, it doesn't take much e2 to cause growth at that point.
Now if you DO aromitase a lot, you're going to need to use an ai just so you're not pounded with higher estrogen sides apart from breast tissue growth. Sex drive, mood and just general health.
So, my recommendation. If you're trying to push every chance of growth and you don't have gyno sides, leave the nolvadex out.
If you are more concerned about cholesterol or, have pre existing gyno, nolva is a better option unless, you can keep e2 in good shape with Aromasin since it's not nearly as rough on lipids.
Igf is important but, there's much more that comes into play building muscle.