They are all sonar. Sonar is just a device that bounces a sound down to the bottom through a water column and then back to the transducer to see what's in that water column at that time. Flashers are more of an instant read sonar. It shows what is going on under your transducer at that second with no past information to clutter the screen. The regular fish finder type sonar will give you the same information but as it scrolls, the old information is kept on the screen as it scrolls. This is good info also but can clutter a screen. I've used both and they both work fine. Basically, you get used to what you are using. I've noticed that on most instances the ff needs a little more adjustments when you move from spot to spot, depth to depth and even depending on lure size, jig to jig. I've found that some small jigs don't show up as well on a ff as they do on a flasher... but that could just be my choice of ff at the time. All things considered, they both will work. The camera is for seeing what's happening below the ice. They can be difficult to position just right but once you do you can have a great view of what's going on depending on available light and water clarity. If you are in stained or murky water, the camera will be useless.
the up side of using a ff is that you can go from ice fishing to boat fishing with the same unit. I have a decent ff with dsi and a flasher mode, but I haven't used it on ice yet. I have a flasher for ice and I'm used to it so why switch, but I would really like to try the ff some time just to see how the dsi, chirp and flasher modes work on ice. Just never had the chance last year to get around to it.