I have killed three in the last four years and used a 460 grain arrow at 270 fps, both fixed and mechanical heads. Plenty flat shooting and great penetration. All my other caribou in years past I don’t recall my arrow set up.
I've hunted caribou the last two years and would recommend that you be able to shoot 60+ yards effectively to take advantage of the typical opportunities. My caribou setup was the same for elk and mule deer last year. Axis arrow with our Iron Will reinforced HIT system and either S or SB series broadheads. 3 fletch with Max Hunter vanes at 3 degrees helical. 510 grains total arrow weight going 285 fps.