many wise words elided ....

How big/heavy are the loads? You might well want a cargo style bike, and/or front and back racks (I have a Stromer, standard rack on the back, a Thule on the front). Do you need shocks to keep the food from potholes? Once you get past determining what frame/shocks will work for you, then test ride a bunch of bikes (ideally, with a model load). DIY may be cheaper, if you are skilled. If you go for off the shelf, plan to invest in a second or third battery. Ideally, cache battery+charger at one of the friendly resturants you do the most business with. Swap batteries long before you run low.

As much fun as Class 3 bikes are, with the range you desire, I'd stick with Class 1 (2 if you really need a throttle).

Oh, you might consider a Burley Travoy ... with soft sided cooler(s) it might be useful. But note, it's pretty narrow (good in that it feels like it's not there, narrower than my shoulders ;>) which might not work for your food loads. A regular trailer (e.g. the Burley cargo trailer) is more flexible ... but much more annoying to park, back-up, etc.

FWIW, over 10K miles, I've averaged <!--td {border: 1px solid #ccc;**br {mso-data-placement:same-cell;**-->0.0269 kwh/mi on my Stromer. I have only a few data points for my wife's new Haibike, but that does seem to be about 2x as efficient (Class 3 vs. 1). Older bikes (and less expensive ones to this day, and probably all DIY) base their dynamic range forecast on voltage. That's pretty poor for LiON batteries ... so bear that in mind as you manage your "state of charge" during a long work day.