Appropriate to meet with prof. to discuss low quality exam
Yes. If you would like to discuss the exam, schedule a meeting and talk with your professor about it. It seems that you have already discovered the core issues impacting your performance here - a lack of sufficient planning and the resulting lack of time - so it may be helpful to consider what you hope to learn from such a meeting. Are you hoping your professor knows some way to accomplish more work in less time? Are you looking for some confirmation that you really couldn't have done better? Your professor may have useful feedback but will likely agree with your assessments about planning.