Right now its mostly about “divide and conquer”. They inject moles into political groups which will then actively push for violence and extremism which in turn causes a split of the group. Another effect is that people that are active in opposition politics are always questioning whether their comrades are on the states payroll (“V-Mann”). The goals here are to 1) weaken opposition, and 2) provide plausible reason for more sate security (e.g. Verfassungsschutz).

(Historically, the Verfassungsschutz was founded after WW2 and its goal was to persecute communists. It was headed by hardcore Nazis for more than 30 years. Even the Americans called it a “phony” institution, since its name translates to “Constitution Protectors”.)

There are rumors that big parts of the Neo-Nazi scene is funded by the Verfassungsschutz. They funded and instrumented the NSU assassinations and the Oktoberfest bombing. That's only what we know of today, go figure.

If there was a fascist regime change in Germany, yes, I would expect a lot of people to be disappeared.

Impact on me personally, right now? How would you feel if there was a military black-ops agency tapping you?

In the past they used it to infect the laptop of a potentially drug trafficking medical doctor.

Of course it's unclear what the secret police is up to. This is mainly for the federal police and customs police.