You should be optimizing after-tax income net of perceived risk; NOT minimizing taxes. 

Special Assessments generally spook buyers so removing this potential objection is always a higher priority than trying to optimize for purchase price / payment.

I have seen that even with optimized VR websites the OTAs will still rank higher, but it is good to be in the ballgame with them there. 

I would focus on buying a handful of high quality B properties (for the optimal combination of cash flow and capital preservation/ possible appreciation) with low turnover and low maintenance costs rather than many lower-tier properties that will likely bring more issues, especially if you have to deal with Section 8 housing authority bureaucracy. 

If it drops it to a number below the ROI you could get elsewhere... why not sell it and take the profit + reinvest in optimal returns?

If so, what areas are optimal for a good cash flowing rental (minumum vacancy rates)?

You can find calculators for this using YOUR income / expenses by searching "Equity Optimization" or "Equity Advantage" input YOUR numbers and get a result.

Get a good web service like investor carrot and either hire someone to optimize it or learn it yourself lile I did. 

I mean negative money is not optimal

Aside from the management, there are many optimizations that are probably lacking which is why one property is drastically underperforming compared to another.