What specific upgrades can be made to a gravel bike to significantly improve its road performance without sacrificing its off-road capabilities, and why do some experts argue that certain upgrades, such as narrower tires or a more aggressive geometry, can actually detract from the bikes overall performance in both environments? Can a gravel bikes versatility be maintained while still achieving road-worthy speed and efficiency, and if so, what are the key component swaps or modifications that can make this possible? Are there any particular componentry or design elements that are often overlooked or undervalued in the pursuit of a gravel bike that can handle both on and off-road duties with equal aplomb?