Alright, so I played a bit of Sonic Adventure. It’s, well, it’s Sonic Adventure. I fell through the world geometry and died in the first stage, haha. The port seems fine. Based on the DX version of the game (Though there is a DLC DX Upgrade available that gives you Metal Sonic). It runs in the correct aspect ration, with a blue border pillar boxing (and very slightly on top and bottom).
It certainly hasn’t smoothed out any of the jankiness of the game, but if you’re expecting Sonic Adventure, it seems okay. Ran at 60fps during gameplay (Xbox One X), and 30fps during cutscenes.
I didn’t get a chance to play Sonic Adventure 2 yet.