All three cases (and more) happen -- and anybody that believes it ain't so, or that "being cozy" (which can make or break careers worth of millions) is of less concern than direct bribe, probably also believes in the tooth fairy.
Why is cozy less of a concern? If you're in with the in crowd, you go places. That might mean socially and professionally. Both of these have financial implications, if finance is your main concern.
Cozy/informal incentives may be even more sinister. At least monetary payments have a hope of being tracked or spotted by someone. A wink-and-a-nod that in the future you'll get some juicy scoop or could land a cushy job somewhere else through a mutual contact if you run some story is pretty hard to spot.
it absolutely is... "access" is a form of currency, sometimes an extremely valued one.
the impact of access is such that the behavior of mainstream journalists can be manipulated toward one's preference through reducing or restricting it (or threatening to do so) - provided there is sufficient value in said access, of course.
Among countless cases, some uncovered, some unknown: http://www.nytimes.com/2006/09/09/washington/09cuba.html
It's no new either: https://en.wikipedia.org/wiki/Operation_Mockingbird
And not just in news either: https://topdocumentaryfilms.com/hollywood-and-the-pentagon/