I need to burn an ISO on 2x, but Brasero only let me burn it on 4x. Is there any way or any app who will let me burn on 2x?
Your hardware is more then likely what is determining what speeds are avaible for you to burn with. I would say that your hardware is determining the capable burn speeds. You can look at your burner and see its capable speeds.
You can get other burning programs such as K3b:
This will install another burner you can try to use and see if it has settings to lower the speed as well.