I'm not nearly an expert, just a hobbyist. I think there is a very wide range of training that gets someone in good enough shape to do well in the mountains. The best type of training: works with your schedule; that you like, so you stick with it consistently; that contains a mix of aerobic, anaerobic, and strength work; and that does not result in injury, such that you can stay in some sort of training pattern year-round and build fitness year-over-year. (Understanding that a training pattern will contain downtime also.)
For me, personally, I like to maintain an aerobic base through running, 30-40 miles a week, do a simple strength routine 2x per week, pushups and pull-ups every day (or nearly every day), and then add on top of that for various objectives. For hunting and backpacking, I do a weighted pack hike one day a week leading up to the season, working on muscular endurance. If I'm running a race, I'll add in intensity-focused running workouts and one longer run per week. Not saying that this is "the best," it's just what I do.
My primary goal is to maintain fitness in the long term; I am deathly afraid of being one of the many folks I see walking around in their 30s, 40s or 50s whose quality of life is limited, sometimes severely limited, by their abysmal physical fitness.