Any kind of abrasive cutoff wheel will likely burn the paint. I would use a square punch something like this and make a series of punches. Or use the punch to punch the two corners and then join them with a body saw with a fine blade. Score the paint on the cut line with a sharp razor blade.
https://www.amazon.com/Q-Max-Q-Max-S.../dp/B07DVFXJJN
I just installed a set of these on a Mustang hood. It will be tricky if there is a second layer of metal brace under that area. The brace will have to be cut back beyond the straight edge by 1/4” or so.
You will need to put some kind of paint on the cut edge to prevent rust. I would use a quality epoxy primer.
One other tip would be to take the time to make an accurate template. I used some chipboard but poster board would work too.
If the basecoat was not activated it will be easy for the clear to lift. Go slow and easy and be prepared with a backup plan to repaint the hood. Not trying to scare you but you need to be realistic.
Good luck,
Don