Burly's Flat Bed is in my house, but , yes if you want to lock up the bike , then walk around with the trailer
those Travoys are OK.
off the bike it's like a Fridge Dolly .. just a lightweight load, folding one, with pneumatic tires.
shopping I just use my Ortlieb Panniers ,
one store knocks off a nickel for every bag of groceries they dont have to supply that bag.