Ya.. when the quests are over.. are there still vampire attacks ?

They did for me and for most people, as I understand. But there may be a bug where they might continue for you. I have not experienced it. If you black out the sun you will get vampire raids on that day.

yes if you complete the dawnguard quest line they should quit.

Cheers

The attacks on walled towns stop, unless you do something to cause an attack ,and you can still get random attacks elsewhere.

Pretty much what has been said. If your game goes well, inside a walled city it will only happen when the sun has been blotched out.

Outside you can still be attacked in caves, or in the wild, just while adventuring.

But you can very well be bugged, and the attacks will continue in the wall city after the quests are done.