The total leagues roster is going to be smaller than 99% of fantasy leagues, you need many starting spots and you are still going to have a deep free agent pool. I'd vote 2 for the hitting and the pitching doesn't matter
I'd also suggest using 2 catchers and playing just an AL or NL only league, 8 team mixed leagues don't seem as fun as 1 league or the other with that few teams. better yet, play both AL & NL only leagues