There are no formal differences between the different kinds of Flash apps you describe. That division is rather artificial. I would say that they are all the same thing - Flash apps.
And yes, Flash apps can be dangerous. If there is a vulnerability in your version of Flash (and there has been loads of those) a malicious app can fool Flash to run arbitrary code. That means that they can do anything they want on your system, such as installing malware. In fact, this is one of the most common methods to spread drive by downloads.
Also, off course, if you give the app any special permissions, like using the microphone, it can use that permission in ways that might not benefit you without even exploiting any vulnerabilities. If you let it use the microphone, obviously it can record everything you say and send it off somewhere. Maybe not great for privacy.
That is why the following is good advice:
- Unless you really need Flash for something (and nowadays, a lot of people don't) just uninstall it and the problem is gone.
- If you don't want to uninstall it, make sure to do the following:
- Set it to block by default so no Flash apps run unless you let them.
- Only run Flash on sites you trust not to do anything malicious (and not to be hacked someone who spreads malware).
- Keep Flash updated.