2015 Tundra and a less than year old ARE. Main purpose of the ARE was keeping the dogs safer while on the highway for 3 months of upland hunting each fall. And to provide a reasonable space for locking up stuff as needed. Its been great for the dogs. Keep the wind off of them and they are quite comfortable to low temps on our out of state outings.
Before I bought an ARE for my 2017 Tundra, the dealer guy warned me that the canopy might not be waterproof. When I asked why, he said that the front portion of the bed was lower than the rails so they would have to build the area up with foam. And water can flow down the canopy, and collect on the rails. If there any gaps between the rails and canopy it will seep though. I bought one anyway.
When I asked about dust, he said that the Tundra was actually pretty good. IIRC, he said the late model GM trucks were the worst. Similar to what K1500 mentioned. The Tundra supposedly has fewer problems in that way.
On my Tundra, I had to use eight clamps to keep the water out with my ARE. With four clamps, I'd get water in the bed. I tried shuffling four clamps around but it didn't work.
I also added a Bed Rug, and if you think about it, it creates a tub within a tub. It sort of seals it up. I didn't get much dust at all but I know a rug isn't an option for everyone. My bed was for hauling hunting/camping gear, and occasionally sleeping in so it wasn't an issue for me. Nice on the knees, and I didn't need to haul tall objects or chicken manure.
The only dust I would see was near the tailgate, but since there was the rug on the floor, sidewalls, and tailgate, it did a pretty dang good job of keeping it out.
The rear window did leak, and I just added more sheetmetal screws which solved that issue.