Paste Swap: swaps the contents of two staves. Swap Voice Contents: swaps the notes in two voices, e.g. Up-stem 1 into Down-stem 1 and vice versa. Note that they can be on different staves! The V shortcut only toggles the notes between voices on their current staff.
Swap Voice Order: swaps the horizontal position of two notes, such as if you wanted to switch the order of these two: