Introduction:
When preparing for the Physics optional subject for the UPSC exam, it is essential to strike a balance between practicing problem-solving and understanding theoretical concepts. Both aspects are equally important and complement each other in a comprehensive preparation strategy. In this response, we will discuss the importance of each and how to effectively focus on both.

Understanding Theoretical Concepts:
1. Building a strong foundation: Understanding theoretical concepts is crucial for developing a strong foundation in Physics. It allows you to grasp the fundamental principles and laws that govern the subject.
2. Conceptual clarity: Theoretical knowledge enables you to have a clear understanding of the concepts, which is essential for solving complex problems. It helps in visualizing and applying theoretical principles to real-world scenarios.
3. Answering descriptive questions: UPSC exams often require candidates to answer descriptive questions that test their understanding of concepts. A thorough understanding of theoretical concepts will enable you to provide accurate and well-explained answers.

Practicing Problem-Solving:
1. Applying theoretical knowledge: Problem-solving requires the application of theoretical concepts to solve numerical and analytical questions. By practicing problem-solving, you can reinforce your understanding of these concepts and their practical application.
2. Developing analytical skills: Regular practice of problem-solving enhances your analytical skills, which are crucial for tackling complex Physics problems. It enables you to break down problems into smaller steps and apply the appropriate formulas and techniques.
3. Time management and exam preparation: Problem-solving practice helps you improve your speed and accuracy in solving Physics problems. This is particularly important during the UPSC exam, where time management is essential. Regular practice will also familiarize you with the exam pattern and types of questions asked.

Striking a Balance:
1. Allocate time: Divide your study time between understanding theoretical concepts and practicing problem-solving. Allocate sufficient time for both aspects to ensure comprehensive preparation.
2. Integrate theoretical concepts with problem-solving: While practicing problem-solving, make a conscious effort to connect the theoretical concepts with the problems you are solving. This will reinforce your understanding and enhance problem-solving skills simultaneously.
3. Solve previous year question papers: Solving previous year question papers will allow you to assess your knowledge and understanding of both theoretical concepts and problem-solving techniques. It will also familiarize you with the UPSC exam pattern.

Conclusion:
In conclusion, it is essential to focus on both understanding theoretical concepts and practicing problem-solving while preparing for the Physics optional subject for the UPSC exam. A balanced approach will help you develop a strong foundation, enhance problem-solving skills, and effectively tackle the exam. Remember to allocate sufficient time for both aspects and integrate theoretical knowledge with problem-solving practice for comprehensive preparation.