Baseline (Widescreen) Solution & Issues
The game is Vert-
But there's a FOV setting in the options menu. You can choose from 90~110 degrees.
Gameplay isn't hampered at 16:10 and 16:9 aspect ratios since 95~100 degrees gives a good FOV for 16:10 and 100~105 degrees gives a good FOV for 16:9 aspect ratios.
You can set custom resolution in the game, so it's possible to set any resolution.
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
Even with 110 FOV, you will see some cropping. But it's still very playable.
Eyefinity / Surround Specific Solution & Issues
Gameplay is heavily compromised. Even with 110 degrees [Max FOV available from options], the screen is severely cropped [To the point where you can't even see half of your gun].
4k UHD Specific Solution & Issues
Works just fine.
But the texts in the console menu becomes very tiny and barely usable. Main menu and HUDs are properly scaled.