You have said it all and for the hive witness stuff, it's kind of easy. If one is a hive witness, it means the person is contributing something to the hive blockchain like the markdowns you see on peakd front-end, it was done by some witnesses.

These various front-end are done by different witnesses and if you like them, you can just vote for them as a way of supporting them and encouraging them.

I don't know everything in details Sha but this is basically it.