What you need to do is look at which genus the gourami you're interested in comes from. Anything from the Colisa genus (from India/Burma/Sri Lanka in the wild) will be very timid apart from when the male is defending a bubble nest that has eggs and/or fry in it. Anything from the Trichogaster genus (generally from south east asia in the wild) will tend to be a bit more aggressive in certain situations. Both Pearls and Moonlights are indeed reasonably peaceful. You will probably be ok with any Trichogaster Gourami, just avoid Betta's and use a bit of common sense, e.g. put fish of a similar size in together.