Your list has fish that grow too big for a 20 gallon tank, and fish that have differing water needs.
Molllies, swordtails and platies are hard water fish, the rest are soft water fish. You need to find out how hard your tap water is, your water supplier's website should have that information somewhere. We need the number and the unit as they could use any one of half a dozen different units.
Pearl gouramis, Bolivian rams and mollies need a tank at least 36 inches long. Swordtails need a tank 48 inches long. So these species are not suitable for your tank.
We need to know your tap water hardness before we can say which of the smaller fish would be suitable.