Question 1: water or not. Water does two things. First and foremost it is a heat sink to keep temps low, generally 215 to 225. You can replace water with sand or clay and have a greater temp range. If you learn to control temps without water or sand/clay, using water is a choice and takes us to the second point.
Water helps more smoke adhere to the meat. You'll develop a taste for how much smoke you prefer. I dry smoke all the time now but it took me a while to figure it out.
Question 2: clean the grates and empty the ash. Use a brush on the dome when you see smoke residue flaking. That's it.