The investment and the account both matter. Check how much you can add, any tax taken from income, access to cash and the tax cost of a move.
For Canadian residents comparing corporate and personal accounts. Cross-border tax residence requires a separate review.
No. Eligible direct US corporate dividends can receive retirement-plan treaty relief. A Canadian fund with foreign holdings, a TFSA, and investments from other countries need their own treatment checked. See Article XXI of the Canada-US treaty.
Not necessarily. A transfer or sale can realize a gain, use contribution room, or require a taxable corporate withdrawal. Compare those costs with any expected future benefit before moving. Read CRA's TFSA contribution cautions.
See why account placement, withdrawals and investment risk need to be considered together.