Layouts and DialogWrapper

I'm building a plugin, like a (Tab)Switcher on steroids.
Now I read somewhere on this forum that I should be extending DialogWrapper. So I did.

So now my question is, how can I get rid of the buttons and the giant border? The standard Switcher is small and lean, mine is bulky.

Also, I'm generating the lists dynamically, by having a GridLayoutManager (Intellij) JPanel and adding a JLabel and a JList per list.
The lists and labels all have giant (well..) borders around them. How can i get rid of them dynamically?

Thanks in advance for your help!