ok so from what I gather .....
1. it will help if you are often in deeper mud/water that might be deep enough to get sucked in the OEM airbox but not likely enough to damage your electrical items.
2. It may help you get out of an extreme situation in a pinch but you might have to sacrifice some electrical items.
3. It isn't really for long periods of deep water fording, at least for our platform.
I did a little more reading and it looks like most snorkel kits have some kind of drain in the air box to allow the rain water to run out.
I think as far the cowl goes, are best bet on our platform is to see how they did it on the 2013 Range Rover. Or do the butt ugly FJ thing, I'll be glad when that ugly thing is out of production. The annoying thing for me, is my four door sedan could easily have had a snorkel, it was just a tube running from the far back of the air filter all the way to the front, coulda just cut a hole in the sheet metal and been done.
For our platform, you have to do something about the air filter, and I believe also the windshield washer reservoir, and air conditioning system. I think JonA or KaRO will be closest to figuring out a solution that way. As far as leaving most of the engine stock... it's going to be a lot more interesting. Though at least a few have done the hoodscoop method for raising their air intake.