Before you start making changes to your cooking setup it’s good to have a reason for making the change. If you’re not happy with your crust or bark on low and slows, don’t add more moisture to your cooking chamber. Were you using any kind of a water tray prior to adding the Weber water pans? Are you wrapping your brisket? I only wrap to stop my briskets and butts from getting too dark and barky. Yea, not a real word, but it should be. With no water pan in a pellet grill I can’t even imagine NOT getting good bark. Most of the water pan users come from past use of a Weber Smokey Mountain where it’s used to stabilize the cooker temp more than anything else. I do use a water pan, off to the side, when I cook ribs on my pellet grill. I prefer less bark on my ribs for an easy bite through on the meat. So much of this is just preference.
On my Ceramic Green Egg cookers I can go without wrapping or water pan for over 20 hours with no issues. Because of heat retention there is much less airflow to dry out the meat. My Weber pellet grill, I had to wrap briskets to stop getting too much bark. Inherently, pellet grills have way more air flow, that in my experience, makes it easier to get bark on low and slows. My Pitts and Spitts pellet grill behaves similar. Yes, adding steam pans under your meat will considerably slow down the bark and burn more pellets heating the extra mass of the water.