I couldn't keep mine moist enough, stupid as that sounds here in FL. But I'm not giving up on the idea.
I've had that issue with every sort of raised bed I've tried here in central NC.
They have to be watered more than once per day in blistering heat.
Same here. Everything gets planted directly in the ground. I also mulch things like tomatoes, cucumbers and flowers.
I do grazing frames for the chickens so they can't tear up the roots.
If you really wanted to try the circles, put a piece of pvc with holes drilled into it in the middle of the stack. That would let you water in the middle and lower parts of the pile. I've set up large strawberry jars this way so the bottom plants can get more water.