What are the key considerations when selecting a top gravel bike wheel bag, particularly in terms of durability, protection, and portability, and do the benefits of a hardshell wheel bag outweigh those of a softshell option for frequent travelers and event participants. How do different materials and construction methods impact the overall performance and lifespan of a wheel bag, and what features should riders prioritize when choosing a wheel bag for their gravel bike setup. Are there any notable differences in wheel bag design between manufacturers, and do certain features such as reinforced stitching, padded compartments, and weather-resistant zippers make a significant difference in the overall quality and functionality of a wheel bag. What role does the size and weight of a wheel bag play in its overall performance, and are there any trade-offs between these factors and the level of protection provided to the wheels. Are there any emerging trends or technologies in wheel bag design that riders should be aware of, and how do these advancements impact the way riders transport and store their gravel bike wheels.