So basically in TSC pressing the pause/break key freezes the game but allows you to freely move the camera around, which is extremely useful for screenshots. Is there any way of doing something similar in TSW3? I've found lining up screenshots, especially on high-speed routes, super difficult.
No. Nothing built in like this. There may be something available while running the game with Universal Unreal Engine 4 Console Unlocker, but I can't confirm it at the moment.