Sirpedrovic

Could be wrong, but pretty sure Fortnite is horizontal clamp only if the aspect ratio is less than 16/9. It's then 16:9 clamped for wider aspect ratios. This is why people use stretched resolutions, because they gain vertical fov and get thicker enemies. So you could do 1208x1080. Same focal length, but render the rest of the image vertically.

Matching the fov means that you are matching everything (tracking, flicking, 180ing) which means that you will be more consistent
If you have diferent FOVs on diferent games you will be compromising in some areas. In your case since you match at 0% you are maintaining tracking but losing on your flicks
What you can do if a game has a locked fov is to use this guide: