Fullscreen: SoftTH (DX9 x86). In-game select massive resolution.
OR Borderless: Edit %LOCALAPPDATA%\PAYDAY 2\renderer_settings.xml. resolution = yours (+ border = borderless), windowed = "true", aspect_ratio = "#.#####" (yours = width / height, ideally including borders). In-game ShiftWindow (same nums & to position). Then increase ShiftWindow nums till borders completely gone. (Mine was left & up a pixel, width +2, height +2.)
(PLP screenshot with bezel effect)
NOTES:
Optional FOV: in-game slider.
aspect_ratio can sometimes simply be set to 0 (auto. Untested).
If thick margins, restarting game likely fix; if not, must correct refresh rate entry in renderer_settings.xml.
View guide for general help with the instructions.