The best export setting for highest quality is to UNcheck "Resize to Fit" — and don't even worry about the pixels per inch, it simply doesn't matter.
If you export full-sized images, with no changes in any of the sizing settings, that is the highest quality image you can export. It doesn't matter what that PPI (pixels per inch) setting is. It has no impact on image quality. It's only real function is to enable you to set a PPI setting so that software such as Photoshop can show what the size of the image will be at any given setting. It doesn't change quality at all.