The reason Nero works so poorly now is because they try to cram too much crap into a single program. So instead of looking for one big fat program as replacement software, look instead to lean dedicated tools:
"Already authored" means the DVD-Video authoring was done in another program, and the VIDEO_TS folder set, or the ISO discs image, simply needs to be burned to a blank disc. The program listed here does not author video.
Sometimes VSO has special sales or coupons. I've seen it sell for as little as $35. That's a bargain, see what the software does -- makes life easier by converting video easily, having very high MainConcept
-like quality, and accepting manu input formats. It's worth it, as none of the free tools are this good.
"Shrinking" DVDs is often referred to (technically) as the process of transcoding DVD9- to DVD5-sized DVD-Video. It makes a dual-layer retail/commercial DVD or otherwise fit onto a standard 4.38GB ("4.7GB") blank disc. This can be useful for fair-use backup, and included several interesting options (Reauthoring, for example), and even has uses outside of "backup".
If there's anything I've overlooked, let me know.
Still current as of October 2013