As Virginia says, you don't need to subscribe to post - subscribing only notifies you of new topics in that forum.
I agree it would be nice if the "Subscribe..." button refected that you were already subscribed. But in the meantime, you can review all your subscriptions from your control panel.
I don't see an option to choose whether your post is to be communicated. That's controlled by whether or not any given user has subscribed to that forum. The only option I see related to e-mail is whether you want to receive e-mail notification of any replies to your post.
You can control in your control panel what the default setting is for the e-mail notification of any replies to your post.
I don't think most users would want a default setting that deluged them with e-mails. I'd think most users would want to follow a few topics, and would subscribe to them, ignoring the others.
I don't think this is the place to discuss beta issues.