Yep, the resolution is 1920x1080, and the format is mp4. I checked my vid again just now, and noticed a delay in the start. So I think you're right that it's not playing as smoothly as we could expect on YouTube. I imagine there's a huge bandwidth pressure in hosting myriad videos, like YouTube does. So yeah, DTube has some growing pains. I feel hopeful though. I'm very impressed with DTube, for the most part, especially because of its solid integration with Steemit.