MTB hip packs come in different sizes and different designs depending on the brand, which makes them very versatile. You can always carry a fanny pack for everyday use or to go hiking, but these mountain bike-specific fanny packs are more useful in other environments. For example, on a bike tour, the fanny pack is the best option to keep you moving without carrying extra burdens. You can take your multi-tools with the water bottle or the water tank if even some spare parts such as tubeless repair kits, etc. allow it.
The MTB hip pack is the best option to stay on the move without carrying extra burdens. You can take your multitools, the water drum or the water tank and even a spare part.