HI. for bbs 0.2 the correction with hex editor is the same as for the steam version of KH 3. both for resolution and fov. the hud unlike KH3 does not cut but the viewfinder behaves incorrectly. I honestly didn't find it much of a problem.

If you already know this, feel free to ignore, but the info might help someone who does not know already :)

I'm relatively green to hex editing as far as super specifics, but I've done it for a while.
The value that is ultimately affecting the ratio is 7B 14 D6 40
This value represents 21:9(2.38:1) or typically a 3440x1440 monitor
Their are other 21:9 monitors since 21:9 is a somewhat blanket marketing term
a 21:9 monitor that is 2560x1080 or 5120x2160 will be more specifically 2.37:1
This means that by using 7B 14 D6 40, there will be thin black bars on the top and bottom of the screen since 2.38 is slightly wider than 2.37
2.37 users should use 00 00 D8 40 in place of 7B 14 D6 40
For 32:9, 71 3D 92 40
These values are determined by calculating 9*(old ratio/new ratio) according to a reddit user, then you flip the values(40 D6 14 7B to 7B 14 D6 40)
These values are not always the way you edit hex values though, not all methods are equal, and in cases that are different from Kingdom Hearts, you can reference these [www.wsgf.org]