Cash on Cash is probably only a measure of the velocity of my money and not performance of the property.

this will offset lower inventory and result in a net retreat of prices to incentivize velocity. 

I’m selling because of the velocity of money.

This will be beneficial if you're interested in flips or the BRRRR strategy and understand the velocity of money and how that can expand your portfolio exponentially.Read Rich Dad's Cashflow Quadrant as well.

I know it is enough to purchase 2-3 investment properties with conventional financing, but not sure if I should use my HELOC to first do velocity banking to pay off most of my debt first (34k student loans and 11k auto loan).

I always encourage real estate investors to learn velocity banking.

If you do this option check out Kwak brothers VELOCITY METHOD.

With the HELOC option, the fees are minimal, the money can be deployed and repaid over and over (velocity of money). 

Do a BRRRR, and then pull your money back out... if all goes well and you're using your 'velocity of money' correctly, you'll have another rental with NONE of your own money in it, thus earning INFINITE returns. 

Remember the velocity of money!