In-game: windowed. Flawless Widescreen (leave bordered). ShiftWindow. Both: increase values same til borders gone (a hint more than resolution + border).

(PLP screenshot with bezel effect)
(An alternative to FWS, but menus stretch: Edit %APPDATA%\DarkSoulsII\GraphicsConfig.xml ...WindowScreen... x2, + border)
View guide for general help with the instructions.
File Attachments:Dark Souls II 2014.jpg