In case you missed something in the acronyms and jargon, there's a few things to look for (assuming you've settled on a 29r, which you should):
Travel - Around 100mm is usually a XC bike, more than that is usually a trail bike, and around 150mm would probably be an enduro bike. It might seem like more would be better, but apart from the weight differences, there's also a pedaling efficiency compromise. On a smooth tar road, a rigid hardtail will be the fastest (0mm travel, like a road bike), and a long travel downhill bike the slowest, even if you're doing the same watts, and everything else is on the spectrum in between. Soft suspension is nice, but it comes at a cost, and that cost is that it takes energy to move that suspension, and that energy usually comes from your legs (assuming a smooth flat road).
Head Tube Angle (HTA) - The steeper the HTA is, the more sensitive and twitchy the bike will be. The slacker it is, the more stable and controlled. But again, compromise. Steeper head angles make bike more nimble and have quicker steering. Slacker head tubes won't steer as quickly, but will be stable and feel planted on rough stuff.
My advice: Look at what 90% of the trails you ride are gonna look like, and buy the bike that's gonna make that the most fun for you. Maybe you don't care about speed and just want to be comfortable - get a trail bike. Maybe you want to go as fast as you can and smash a race now and then - get and XC bike. Maybe all you're ever gonna ride is a jeep track - a hardtail is probably good enough, but a dual sus will be kinder to your bum. Each bike is perfectly suited to a terrain and riding style, and is going to be a compromise on everything else. An XC race machine is exactly that - a race machine. So short travel for efficient pedaling, and steeper head angles for quick steering. An enduro bike is great for gnarly terrain where you don't mind compromising a bit to have a softer ride and more stable handling. A trail bike I guess is somewhere in between.
I made the switch from being a roadie to mountain biking in December. Got myself an Epic, and put a dropper post on it (which I would highly recommend). For me, it's the perfect bike. Living in Pretoria, a lot of the riding I do is gravel roads, jeep track, and non-super technical single track, and the 100mm travel is perfect for that. On more technical stuff, I use the dropper, and try to pick good lines.