For a GEM, once the computer is aligned leveling the mount or tripod makes no difference for GOTOs operation. But a mechanically plumb tripod or pier is more stable, settles faster and your elevation and azimuth mount alignment controls will make true movements not diagonal which makes polar alignment easier to nail more quickly.
For an Alt/Az mount leveling the mount is typically fairly important for single star GOTO performance unless you are going to shoot multiple stars to build a model to compensate for the mount's leveling error but even then a level and plumb mount will work better.
Chip
