There will be a pouch that fits a 2m chain - There are ones that fit 3 metres in!!
The straps all have male end QR clips. Therefore, they will not clip into each other.
Typically, to hold the fully laden pouch tight to the back seat, the straps will be adjusted so tight that when the pouch is not clipped on, the clips are flush with the seat. They don't dangle in the slightest.