Power O.I.S. is supposed to bring even better stabilisation. I can't say to what extent this actually helps with the 30mm lens. In any case, the mega already works with Dual IS.
I use the lens with the G9 - no problem. Splash water protection rather not (https://www.digitalkamera.de/Zubeh%C3%B6r-Test/Testbericht_Panasonic_Lumix_G_Macro_30_mm_2_8_Asph_OIS/9709.aspx).