It depends on what boat it is (obviously!). Spring 25's will take the ground as they have twin rudders of the same draft as the keel. I suppose the wider the wing the more stable the craft would lie.
As Keith says it depends upon the boat. My Parker takes the ground quite happily because the wing keel lifts and is designed to carry the weight of the hull on two strong points which rest upon the top of the wing.
If the boat has a fixed keel with wing on the bottom I would not treat it differently to an ordinary keel. Even if the wing is quite large it will almost certainly not be stressed to carry the weight of the boat other than vertically downwards. It will not have the area to make the boat stable if not shored properly. Simple mechanics say that once a vertical line from the centre of gravity falls outside the area of the base it falls over.
It does too!
It may sink less in soft mud than an ordinary keel because the pressure is much less being spread over the area of the wing. On the hard it will need to be shored in just the same way as a normal keel.