Anything really happens in the clubs?

All the events advertised actually take place, unless something really unusual happens. We do have a look at which clubs the JOYclub partners with and you can see the seals of approval or star ratings on their site. So there will be a party if you show up, of course it is also up to you, what you do with your time there.
As a new comer I can recommend giving it a try, but manage your expectations. Like go there with the intent to figuring out the place and having a nice evening. Of course play can happen, but it is not garanteed. Talk to people also, get to know the scene a little.

In my experience, as long as you are clean and respectful (and clean!), you should have a good time.

At least in Switzerland are correct.

Yes. I've been to several events in the Stuttgart & Heilbronn area and there is fun to be had. As a single male, I am always respectful though and don't force anything.