I've put many accessories on my bike to make it very easy to run errands. Many of these accessories I simply transferred from my conventional bike to my E+.
1. BobYak trailer. (mine is over 10 years old) I transferred my connection hub from my Mountain Bike to my E+ without any modifications.
I use it for it for trips to the store when I intend to bring something oddly shaped or bulky home. I will use it for work when I want to bring in a large cooler for special food. I even once used it to carry 2 bales of hay....people looked at me & must have thought they were in a 3rd world country! Its also great for camping. I never take the hub off, it stays on so I can easily connect the trailer & go.
2. Detours Town & Country front basket. I use this daily. It carries groceries from the store or anything that will fit. Its advertised as being capable of carrying a "micropooch" up to 8 pounds. Mine is about 3 years old. Its very convenient with its quickclip attachement, handles & drawstring top. Its very thoughtfully designed & built. No modification was necessary to attach this to my e+ bike.
3. Rack: SunLight Rack with spring clamp. I believe it can support up to 22 lbs. Mine is about 3 years old. I find I'm constantly wedging extraneous things under the spring clamp such as a lunch pack or a "Bundle of Warmth" package of logs from the grocery store for the fireplace. I've had no problems attaching any of my various bags to it. I did have to modify the the rear frame attachment on the left with a longer screw to accomodate space constraints introduced by the back hub attachement for the E+ motor. It was an easy modification.
4. Bags for shopping & bringing clothing, etc. to & from work: Basil Mitre Shopping Bags. I use these every day. They're very easy to come on & off the rack, stable, very water & mud resistant, easy to pack & unpack & pretty. I like them so much that I use one of them off the bike to carry my purse & laptop when I travel.
I've tried lots of other products over the years. These are the ones I've found most usable for my errand running & commuting needs, and they work well on the E+ bike. I have the mountain bike frame.
Hope this helps.
Heather