Charles Russell did a painting of a bear over a downed ram. I think it was titled “Who’s meat”. I was partial to it. I don’t hunt the park boundary area (Island Park) country. So I haven’t been to interested in a grizzly hunt. But I am hearing they’ve been protected long enough the fear of rifle fire signals meat on the ground to them instead of a flight response. We have a few grizzly / hunter episodes every year. Sometimes you get the bear, sometimes the bear gets you. Idaho is grizzly country. People need to act accordingly.
As far as caliber for grizzlies bottom of the scale to me is 300 win-mag then up. Emergency 12ga double 00buck alternating with slugs. Your friend backing up a hunt. Marlin guide in 458 win or similar Hiking with a friend a 22 pistol and tennis shoes. The biggest wild card is they meet you when neither of you expect it.