74 minutes was the original max length. Then it went to 80 minutes but not all discs, CD burners, and players support up to 80 minutes. In fact, if you do a CD duplication or replication order and there is over 74 minutes of material, most places make you sign a wavier saying they are not responsible for problems.
If it’s for personal use, I still think you’ll have a problem doing any burning beyond 80 minutes. I don’t think WaveLab (or any app) will even allow it.
To answer your first question, just get WaveLab Pro and you will have all the features you need. I would find WaveLab Elements too restrictive for most work.