My angels are 15-20cm nose to tail and the same upright as well! They wouldnt fit in a tank that size, people just dont appreciate how large angels can get, they keep growing late on in life!
From personal experiance, with apistos, i would go for one male and two females as it then spreads the harassment from the male out, then if they do pair up, the lone females seem to be happy mooching about on their own!
Another few species i like are Nannocara Anomola, Nannacara Aureocephalus and Laetacara Curviceps