Yes and No!
I have a MES which I use most of the time.
All my smokers have some sort of water pan.
All of your questions are answerable by either yes or no depending upon who you are talking to at the time.
Some spritz, some mop some do neither. Some use the water pan with water, some use it for a heat sink with sterilized
sand, some with beer, some with juice, some do not use it at all. All these different opinions are right. You just have to find the combination that suits you . Its all part of the art of smoking.
Once you have the basics down its kind of a freeforall on what method you use. If I used a mustard coating on the meat then added the rub I will not spritz at all, if on the other hand I just used the rub alone I will spritz 1/2 way through. If I used worchestershire sauce to wet down the meat then put some rub on top of that I will spritz once only after an hour and a half into the smoke. There are many variables to this thing we call smoking. If you do spritz or mop its a good thing to hold off 1 1/2 hours to two hours so the bark will harden a bit thus will not be washed off.
I personally use water in the pan in all my smokers, I believe it evens out the temps in the smoker. I cannot prove that, but I just think its so. I fill the pan right to the rim with boiling water, its very important to have it boiling so it doesn't take an eon for your smoker to come up to temp. It will then last usually throughout the entire smoke without needing a refill, unless you're doing an all night brisket in which case it will need one re-filling. I use a long nosed watering can for refilling. I once decided to move the smoker to a different location mid smoke. Incredibly bad idea, water slopped onto the element and the wood chips and ashes. It made thick billowing hot grey steamy smoke and totally ruined a whole load of meat. Just a heads up. You have to take the water pan out if your even just shifting the smoker.
Oh and Don't worry about asking questions, a Whole lot of us enjoy the heck out of answering them myself included.
The payment for answering your questions is of course qview and the hope that as you develop your skills you will pass them on to the next generation of GnuBees err make that Newbies....
Lots of helpful stuff in this link for the newbies.http://www.smokingmeatforums.com/forums/showthread.php?t=81585