ShellyAnn,
We didn't forget you!

No, they are not in parallel. Though, curiously, when they are off, you can turn on any one panel.

It is simply the easiest way to plumb them. There is NO reason not to plumb them in parallel. However, the piping may get a little complicated. You will have to set up two pipes or

If you go back to my rules of thumb (Just over the Leaning Tower of Pisa), they will work for you...nothing either Richard or I have said really contradicts that.