Baseline (Widescreen) Solution & Issues
Native. Select your resolution from the list in the options menu. The one pain is that you have to exit the game to change the res.
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
For 21:9 you need to edit the Registry.
Go to --> Computer\HKEY_CURRENT_USER\Software\Asobo Studio\Ratatouille
Change VideoResolution:
For 2560x1080 put 4380a00 in.
For 3440x1440 put 5a00d70 in.
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Optional higher FOV via hex edit: Open overlay_win2k.exe via hexeditor.
Look for 00 00 BE 42 (FOV 95) to 00 00 DC 42 (FOV 110) - see Additional Screenshots.
Eyefinity / Surround Specific Solution & Issues
Go to --> Computer\HKEY_CURRENT_USER\Software\Asobo Studio\Ratatouille
Change VideoResolution:
For 5760x1080 put 4381680 in.
4k UHD Specific Solution & Issues