About Shout Box: if you create custom messenger blocks on different pages, it will use Page title as title for the talk by default. We will add ability to edit titles of the talk in the nearest version. You may remove Page: prefix in language keys for messenger in Studio->Polyglot
About Post area text: You may see it on your first screenshot Message... title. You can also change it via Polyglot.
I would like separate page Shout Box massages to not be included in the messages in Messenger. I want people to eventually upgrade to a different paid level or use credits to get access to Shout Box and I also want people to travel to the separate page to view Shout Box messages. Otherwise it defeats the purpose of a separate page/module for Shoutbox and looks too much like a Group message system