I have a nice MTB hydration pack (Source,) a nice trail running hydration vest (Salomon,) and a hip pack (inov8.) For riding I’ll grab the hip pack first, the vest second and only the hydration pack when I have to. The best can take the same as the backpack, but stays put.
The hip pack does move a bit, but it’s still way better than the mtb hydration pack. On the hip pack I can pack a bottle, phone, keys, bars and gels, lightweight warm top and a first aid kit. If I take out the top I can add a second 500ml soft flask. But usually it only has a bottle, pump, phone and keys in it.
try the hip pack, it might surprise you.