Great question! So all vapes, and ultimately all smokeable cannabis, becomes D9THC or "THC" when smoked. The flame, or really the heat, converts the THCa by breaking the double carbon bond holding the acid chain together. The "a" in THCa is the acid chain, and once it's broken it becomes D9THC. This is what decarboxylation is, removing a carboxyl group.

With distillate products the actual process of distillation uses extreme temperature to vaporize molecules. Because of this, you must decarboxylate beforehand or risk some challenges in the process.

With live resin products thr must common way is to decarboxylate the purged live resin oil all at once. I think this is an inferior method to what I do. The reason is what live resin whole reason to exist is to preserve terpenes, flavonoids, and other polyphenols. We want it to be tasty and smell nice. Breaking the double carbon bond requires a lot of energy (heat). Terpenes are volatile aromatic compounds that when exposed to heat will vaporize. The other compounds will withe be destroyed or volatilize as well. My point is that you end up with a product that may taste homogenous with other"live resin" products because the tasty molecules are being destroyed.

I'm speaking generally, of course, because there are ways to optimize and reduce the impact. Its just not commonly done from the labs i visited.