how would i burn i custom ISO dvd or cd for a softmodded xbox can read? such as apps, roms, videos, and music?

Do you just mean burn? or do you mean create then burn?

If you want to create an image then burn it use craxtion4 or qwix to create the iso then just use a simple burning program like ImgBurn for example to burn the image.

Its pretty self explanatory in Craxiton and Qwix on how to make the images, just go to create iso and browse the folder you want to make into an iso and click save then done.

I've found I never had to do anything special for burning videos for the xbox to read them i just burn them straight to the disk. Aka i never had to make an XISO with the video files using Qwix or Craxiton i just used ImBurn to burn the files straight to the disk.

I'm not sure about music though you would have to try and burn a disk the normal way you do it and see if it reads.

For Games and Apps and Roms I believe you Need to Use Qwix or Craxiton to make an XISO then burn using something like Imgburn or whatever burning program you use.

I used Extract XISO v2.2 and used img burn to burn the iso. Does it have to be a dvd?

DVD-R burned at 4x or slower is the most readable disc on an Xbox. All other disc types are somewhere between flaky and unreadable.

Yep Heimdall is correct using blank dvd's is the best bet