1. You don't need to go for stamping, if you intend to join the Canadian firm.
2. Keep the H1B related documents (I-129 petition copy, I-797 notice of approval) with you, if you wish to seek H1B job in US later.
3. B1 stamping has nothing to do with H1B.
4. I had been to these 2 countries once each on short term only (3 months) and hence cannot comment on life there.