I would live with the gap. We needed to replace our refrigerator and the height of the cabinet significantly limited the choice of refrigerator we could use.

Best to order cabinets with the standard dimensions. The freezer needs a gap for air circulation. A 7" gap will not look odd. Worst case scenario: you replace the freezer and the only available one is taller than your current freezer and is too tall for a custom cut-out. Best case scenario: the home is easier to sell with standard cutouts. There is such a thing as over-customizing a home,

We have a chest freezer, but half the size of the full chest freezer. It's in the laundry room with standard size cabs above. Plenty of room for the lid of the freezer to open. There's only two of us so it's a perfect size.

Allow for the 72" height as all freezers eventually die. If you don't like the gap, add a removable panel.