Torch height is more critical than arc voltage.....adjust your height control so the height is as the Hypertherm manual suggests...and ignor the voltage setting. Many THC systems are calibrated differently.
You can cut 3/16 very well with the FineCut part...even though the specs say maximum of 10 ga. Many people use them up through 1/4"......pierce height and pierce delay times are critical on thicker than 10 gauge....pierce as high as you can, and allow enough time for the arc to be fully through before motion starts.
For best angularity on any material...use the lowest amperage consumables. If I wanted the best holes on 1/4" I would use the 40 amp shielded parts, I would program the THC to lock at the cut height (no arc voltage adjustment on any hole under 1" diameter)...and I would program the cut speed for all holes under 1" to be 60% of the optimal cut speed listed in the manual. This will minimize taper. To eliminate taper.....you need to go to a Hypertherm HPR system with a new technology called "TrueHole"....but thats will put you up in the industrial price range!