The top banner color is determined by your genre. e.g. purple for fantasy.
Readers technically get a notification, but it's very lowkey and easy to miss.
No notifications for new subs. There is apparently a notification for new comments, but you have to turn it on, and I forgot where you turn it on. I think it's glitchy though; I'm pretty sure I turned it on when they introduced this feature, and I have gotten no notifications about it.
You can't see who subscribes. The readers are very anonymous, which has pros and cons.