Hello! The game works flawlessly and you get exactly what is advertised, and even more than that.
Regarding technical stuff, I'm not sure which platform you are streaming from but if it's from PC, you can add different sources, including music, inside TikTok Live Studio.
As for the game's size, it automatically adjusts to maintain proper proportions, so you can maximize the window to any resolution you desire. In TikTok Live Studio, make sure to adjust the source size to fit the screen so it will be displayed in fullscreen.
There are many tutorials on YouTube regarding the use of TikTok Live Studio and streaming on TikTok in general. If you need further assistance, please contact me at livegameyouplay@gmail.com. I would be glad to help you out. :)