So I have a rental property which is under a conventional loan but yet it cashflows with the current tenant.

If someone has the credit score, down payment, and debt-to-income ratio that fits conventional standards then they will be able to buy multiple properties personally at once.

You would have to purchase one as an investment property - with conventional a 25% down payment is required for a MFR. 

Several times I've changed the purchase price, repair estimated costs, as well as financing details (interest only payment vs. not, amortization over 30 years vs. 1year for conventional vs. hard money, etc.) and the ROI still hasn't went positive.

With conventional;For a SFR you can do a max LTV of 75% to cash out.For a MFR you can get an LTV of 70% for a cash out. 

5% Is the conventional route.

When I sold the new owner was able to keep the name and flower logo, etc. 

We've got over a dozen of properties loaned with conventional mortgages and at this point it's getting more difficult to get advantageous rates for additional properties.

My concern is how do I have the personal protection of an LLC if I essentially cannot get conventional financing or transfer the title after the purchase?

I work closely with on of the branch managers in Queens, New York.They've done 5% down conventional loans for house-hack clients of mine and can also finance condo deals.