I don’t think so. Part of it is that chests tend to have more insulation (also the reason why mini-fridges are absolute dreck efficiency wise), and the coolant

I don’t think so. Part of it is that chests tend to have more insulation (also the reason why mini-fridges are absolute dreck efficiency wise), and the coolant / radiator circuit won’t be set up properly: in a traditional vertical fridge the coolant circuit is through the back or racks (for freezers) and the radiator are on the back, if you lay it on its back the radiator is now on the bottom, and trying to heat up the insulation, with the coolant circuit also at the bottom.