We experimentally demonstrated doubly resonant oscillator (DRO), signal singly resonant oscillator (SSRO), and idler singly resonant oscillator (ISRO) ZnGeP2 (ZGP) optical parametric oscillators (OPOs), respectively, pumped by a 1kHz Q-switched Ho:YAG laser. At the full incident pump energy, the ISRO got the highest output pulse energy of 8.38mJ and the best beam quality factors Mx2 of 2.3 for idler (4.6μm) and 2.7 for signal (3.8μm) but got the highest threshold of 3.97 MW/cm2. The DRO had the lowest threshold of 3.12 MW/cm2 but had the lowest output energy of 8.29mJ and the worst Mx2 of 3.9 for idler and 4.1 for signal. The output laser characteristics of the SSRO were slightly worse than those of the ISRO. The experimental results show that the ISRO is the most suitable resonant regime for high brightness mid-infrared ZGP planar ring OPOs pumped by 2μm nanosecond lasers.