If I understood you correctly, you were disappointed with the Wallmart bike because you spun the wheel by hand and it didn't spin very long. That could be a minor problem...brakes a little off centre and rubbing on the rim,
when I say I spun the wheel, I did it with the bike upside down and the wheel unscrewd from the frame. It had nothing to do with the brakes.
or axle cones slightly over tightened
That's what I also thought, but when I loosened the axle the whole wheel just became wobbly, it didn't make it smoother.
But this Murray bike that I have, it's a smooth spin.