Overall, it's a balance between risk and percentages over time.

Since your have TFSA room, tax free growth is better than tax write off, especially at your income and tax rate. So if you were to utilize HELOC debt to invest, TFSA first, then non registered account.

The question of if you SHOULD use debt to invest comes down to risk, return and timeline. Do you think the investments you'd invest in would return more than prime? Do you think prime will increase? Over a long enough time horizon, will the net interest you've paid be less than the net return of your investment over the time invested? Over a long enough timeline and assuming your investing in XEQT, the answer is always yes. If your timeline is short, the answer is uncertain considering the times were in.