ppg helical will hold almost anything you can throw at it. Yeh you sacrifice some strength, but not enough to be worried about it breaking. Id worry about other things breaking before any of the ppg gears break.
Absolutely. While straight will hold up to more and more abuse, a good helical gear set can hold a LOT. For example, in a GTR, a good helical gearset will hold 8-900 no problem. The stock can go at 4-500 with a hard 3rd gear shift.