I’d hazard a guess that most of the losses are from when you open the door and the seal around the door. Also while cooler than ambient my fridge and freezer don’t feel cool to the touch so I think that the walls are thick enough.

Otherwise fridges and freezers would ship with thicker insulation.

There's a tradeoff between thicker insulation and space in the freezer

Putting the fridge in the basement probably leads to you opening the door less.

if they are cooler than ambient (cool on touch) - it'd cause condensation.

Even 1-2 degrees difference can waste a lot of watts over such a big surface, and would be difficult to perceive.