Yes, from my understanding every single member of the WGA is striking even if they weren’t working AMPTP (which includes giants like Disney, WBD, Universal, Paramount, ViacomCBS, FOX, Netflix, Amazon and a bunch of others). They are still allowed to work in areas that don’t fall into the WGA’s representation such as personal youtube channels, podcasts or other forms of non-writing work, but they are advised to consult with the guild if the line is blurry. For example, Adam Conover is a member of the board and negotiating committee, and he is still doing his podcast since it’s mostly a self-employed interview podcast, but has directed it towards talking about the strike itself. I think they may even be allowed to direct given the DGA quick agreement, but I’m not sure how one would direct without a writer.

Edit: punishment can range between fines to outright expulsion, but it’s rare for something like that to go through because you also get known as “that shitty scab” to all your coworkers and nobody wants to be both poor and hated.