technically maybe you could do what you describe with front matter in one collection file but that would be a little ridiculous.
A data file could do what you are asking for, you could have a limit when you loop over them to do just the most recent ones.
Looping thru data files is more or less like looping thru collection items, main difference being that you can’t output data items to their own page, you have to loop over them on a page.
Main issue with a data file is formatting - it can be a little annoying to write in yml or even worse json. But it would be easier than making a new file I think.
Have you looked at data files?
as for my initial suggestion, the styling could be handled by classes and that would separate the content from the styling to an extent. But there would be no easy way to do the most recent 5. I would find this method easiest to add new items to, just not easy to do other things with like the new items thing
You could also use JS and store the news items in an actual db but by then you might want to use something other than jekyll.