Social Feed, Announcements and Crowd Pics are the same page type with different settings. Whichever one you added, you can change any of its settings at any time. You do not need to add a different page.
Where the settings are
In the Editor, click the gear icon next to the page in the page list on the left.
Publish your app after you change a setting, so the change reaches people who already have your app.
What you can change
Who can post — everyone, or admins only
Comments — on or off
Likes — on or off
Layout — a list of posts, or a grid of photos
Push notifications for new posts — on or off
What each page starts out as
These are starting points, not fixed types. This is what you get before you change anything.
Social Feed — everyone can post, comments and likes on, list layout, notifications on
Announcements — only admins can post, comments and likes off, list layout, notifications on
Crowd Pics — everyone can post, comments and likes off, grid layout, notifications on
So if you want an Announcements page that people can comment on, turn comments on. If you want a photo grid that everyone can post to but nobody can comment on, that is what Crowd Pics starts as, and you can switch it to a list later if you change your mind.
One thing you cannot change
Posts are made from the Yapp app on a phone or tablet. You cannot write a post from the online editor.