If you are pleased with the results at box speed and you need box speed then use box speed. The general consensus is that you probably sacrifice shadow detail unless you shoot at max 1600 and maybe 1250. Some say the true speed of D3200 is max 1000

For what I think is portraiture in your case I'd use the slowest film I could get away with. In 135 D3200 is in my experience quite grainy with even 5x7 prints and if you intend to print larger than this then making a virtue out of grain is worthwhile

Frankly what counts is what you want and if D3200 delivers this then what other APUGers say is largely irrelevant