Whats the impact of cooking with an empty water pan in this cooker? Do you need to wrap meat? Or i guess how does it change other aspects like temp or style of cooking in the smoker?
There are two reasons (that I know of) that people put water pans in a smoker. First is to keep the cooking environment humid. You can google this and find lots of argument about whether or not it's necessary. I'm not going to argue that either way, but I live where it's always humid and don't find a big difference in the outcome either way.
The second reason is to add thermal mass. Thermal mass absorbs heat when it is at a temperature less than its surroundings and radiates heat when it's at a temperature greater than its surroundings. Adding thermal mass to a smoker means it takes longer to heat up to your target temperature but once it's there it tends to stay at that temperature: too hot and the thermal mass absorbs energy; too cold and the thermal mass radiates energy.
So to keep a cooker at a nice steady temperature, more thermal mass is better up until the point that it's just takes too long to heat the cooker to temp. Water pans are nice to add thermal mass for a couple reasons. If you just add more steel to the cooker the thermal mass goes up but so does the weight. Since water is pretty easy to get and get rid of adding water when you're cooking and getting rid of it afterwards adds thermal mass without increasing the permanent weight of the cooker.
When you're smoking low and slow, water has another 'magical' property, Add heat to water and it heats up until it's at its boiling point - 212F at sea level. Keep adding heat and it evaporates but it doesn't get any hotter. So now you have a thermal mass that's very close in temperature to your target temps and will not get any hotter. Perfect.
On the other hand, dealing with a water pan can be a hassle. You've got to put the water in there and dump it out afterwards. As the water pan evaporates the amount of thermal mass in your cooker decreases. Let it boil dry and you can get a big temperature spike. Add a bunch of cold water and you get a temperature crash. And if you're trying to cook hotter than 212ish, you've got this thermal mass that's constantly trying to suck heat out of the cooker.
So, some folks forego the water and use other things for thermal mass - sand and firebricks are both popular. Fill the water pan with them and cover with foil. Easier clean up. Sand and firebrick will get hotter than 212 - whether that's good or bad depends on the temp you want the cooker.
For me, my Qubed Pint has enough thermal mass for the cooks I've done so far without adding water or anything else. If I really loaded it with meat or I needed to open the door a lot I might find out it doesn't recover fast enough but no problems so far.