I have hunted woodland caribou a couple of times on the isle of Newfoundland.
As said, and you probably know this already, proper shot placement is the key with any shot.
That said, they die very quickly. My friend got a pass through with a 42# target bow, the P+Y animal went down in 50 yards running.
Same for most of the others, died quickly.
When we cleaned the animals, we hung the bones in trees at camp and shot through them with different weight bows. Even the 42# bow was blasting through the fairly soft bones.The animals are not that big either,bigger than a deer but nothing like an elk.
Be prepared for a moving target, they do not migrate, you have to find them. When you do, they are constantly milling about. Do not make a noise to stop them, I have seen this backfire most times. Don't be discouraged either if you dont see them for a few days, suddenly they will be right in front of you.
Good rain gear is essential, great binoculars are a huge asset. Waterproof, fog proof.
There were a pile of ripped rubber boots at the end of the weeks, the tundra-like land is very scraggly and can tear through rubber easily. I wore 13" Schnees and oiled them nightly with pitch blend or mink oil.
A lot of guys in camp wished they had my boots.
KEEP YOUR FLETCHING DRY!!!!!
Good luck, one of the most fun hunts I've ever had.