Q:

What calibration options should I look into given these defects

I printed a temperature calibration cuboid for Hatchbox 1.75 mm PLA, in 1 °C increments from 180 °C to 190 °C. 
I have two questions related to this image:

I'm not seeing any difference in quality across the temperature range. Am I just way off base and need to be substantially higher?
How do I get rid of the small layer shifts you can see across the board?

Printed on a RepRapGuru Prusa MK2 clone.

A:

Your print does not suffer from layer shifts as you call them. This uneven layer deposition is typically caused by the (positioning) accuracy of your printer. All-in-all, this print does not look so bad. You would get better quality prints on a different style of a printer; most high-end printers have a lowering platform instead  of a forth and back moving platform.
Although 180 °C is at the low side of printing PLA (usually it starts at about 185 °C), the print does look okay. However, looks can deceive, it does not say anything about structural integrity (layer bonding).
Note, to calibrate the temperature using a temperature tower, you need a different calibration test print, preferably one that tests overhang. This latter is usually far more important as there is normally not much to see at the walls, you need a slanting part in the print or an overhang to determine the optimal temperature.

