So there’s 2 settings:
Reverse Cleanup Bags = C_Container.SetSortBagsRightToLeft()
Loot to Leftmost Bag = C_Container.SetInsertItemsLeftToRight()
Both are character specific and disabled by default.
Reverse Cleanup Bags
Disabled
Enabled
I don’t currently have greys on that toon but if I did, they’d be sorted to the bottom right with it Enabled.
Loot to Leftmost Bag
Disabled: stuff fills your backpack first (top) and then your additional bags (towards the bottom).
Enabled: stuff fills out bag 4 (or the most you have) (bottom) then fills towards the backpack (top).