What's considered the default Isometric Control Scheme?

When moving the character forward do they move;

  • vertically up the screen (up is up, down is down, etc, moving diagonally requires diagonal input)
  • diagonally up the screen (usually up and right is considered the way ‘forward’)
  • in the direction the character is facing (tank controls)

I’m considering trying tot make a beat-em-up style game, but instead of being a standard side scroller, being more isometric, which gives a little bit more screen space for the fighting areas.
Problem is, would the isometric control scheme and the controls for different fighting moves gel together? If they don’t then I’d need to decide to either go back to the standard side scroller, or instead change to 3rd person.