Using Nero Express?

Not fully clear, what’s better use to burn data DVD, Nero Express or Nero Burning ROM? Or Nero Burning ROM for burning ISO mainly?

Whatever you find easiest. Personally I rarely use the Burning ROM, I find Express much easier.
For burning ISO images I only ever use ImgBurn, never Nero.

My first choice is Nero Burning ROM then for Copyto Copy some times I use Nero Express and for those file that I need to encode first to make compatable format I use NeroVision.

We can use Nero Burning ROM when we have ready ISO image only?[in DVD-ROM(ISO) mode].

Yes but ImgBurn is better.