For speed question, you shouldn’t exceed 8x although Taiyo Yuden have been strongly tested for higher speed.
As eric mentioned, you could use DVD-Lab Pro. Its well designed and offers a lot of pro features and functions that others like DVDSP and Encore don’t, and its just 199$. DVDit 6 Pro is great on PC, with little less features. These softwares are affordable, if you want more, there is expensive Sonic Scenarist or you could buy a used Sonic Fusion system (Mac OS9). I use Fusion and it works really great, one feature I love is the Verify tool that tells you if something does not meet the DVD specifications in your project.
Don’t fear the tiger, the Cow is near!