RE: Is a 270 big enough?
 

I would use it for all butbthe bigger bears!

RE: Is a 270 big enough?
 

Seeing you asked for opions you can have mine...;)

I have a scoped .270 and believe with proper shot placement it's certainly able to handle your hunts mentioned.

I also have a .30-06 with iron sights for brush / stalking / still hunting that I can attach my scope (if needed) onto if I decide to go for the larger game like Bear or Elk.

If your looking for one rifle, than I agree with a few others, that the .30-06 is probably a more versitile load. Good luck and have fun!