Yes and no.
Networks won't help your channel grow. They provide tools/features to better understand and improve your content, which could lead to gaining more viewers and subscribers. But simply joining a network won't help you grow.
Networks do have forums, and you can get subscribers there, but the network has nothing to do with helping you grow. So yes, you can gain subs from the forums, but I wouldn't Join a network for it. You'll be better off here at YTTalk anyways as 99% of people on those forums don't care about others, and are only there to promote themselves. I'm with the network Fullscreen, and the forums is filled with spam. No one watches anyone else's videos, it's simply a bunch of shameless self promotion that leads No where.