Limit amount of adding a certain Paragraph per Content type
Things which only should be unique to a node, should better be attached directly to that node.

There's already a feature request on DO. But I'd recommend you to solve this by attaching these things directly to the node, with standard image or text fields.

-- node type
  |__ hero image field
  |__ intro text field
  |__ paragraphs field


The only other alternative I see is to add multiple Paragraphs fields to your content type and then limit them to only one type and one item.