I can't answer your first questions but I've wondered the same about your last question. When they aren't flowering they look similar to me from a leaf perspective. The picture you took is of a Rhododendron Maximum or American Rhododendron (or also known as "Pete's fly stealers"...). http://en.wikipedia.org/wiki/File:Rh...on_maximum.jpg
The flower of a Mtn Laurel looks like an umbrella (http://en.wikipedia.org/wiki/File:Kalmia_Latifolia.jpg
) and the Rhodo has five major petals. We also have Catawba Rhodos and probably a few other sub species.
The Mtn Laurel is a part of the blueberry family and Rhodos are part of the Heath family, closely related to Azaleas.
That's probably more than you wanted to know...or more than I should know...
Ok, here's a bit more. I just asked my wife about the other two and she says that the first one looks like a Trout Lily (that's an interesting coincidence...http://en.wikipedia.org/wiki/Erythronium_americanum
) and that the second is Bee Balm (Monardo - http://en.wikipedia.org/wiki/Monarda
Now, I need to go have a beer, sharpen my axe and change my spark plugs...