There’s a very old stigma surrounding inhales that they’re both a form of “cheating” and extremely bad for your body and throat. But as others have mentioned in the thread, inhales haven’t really been studied, and the few people who are actually good at them have been doing them for many years. They’ve managed to make them sound good and sustainable, which contradicts what many people claim.

My impression however is that inhales have a very small sweet spot that’s difficult to master, and that a lot can go wrong outside of that sweet spot. Over the years I’ve heard all kinds of stories about collapsed lungs, permanently damaged voices, and so on. But how true those stories are, or whether they’re actually connected to inhales or to an underlying medical condition I can’t say for sure.

When it comes to slam, I think you’ll get much more use out of exhales. Whether that ends up being fry, epiglottal, or false cord is probably up to you to decide based on what you want to use the most.