What one should I get?

Ok, I have a 20 gal planted tank, with 7 guppies(may b getting rid of some) 3 red wag platties and 1 male blue neon dwarf gourami and some shrimp, I want to get 3 swordtail for the tank, 1 malE 2 female. what is the best kind of swordtail for my situation and that won't mess with my other fish and NOT eat my precious shrimp that I like a lot!?!?!?also, along With getting 3 swordtail, I want more red wag platties, so should I just get 1-2 more females or 2 more females and another male? I also read that the red wag platties rapI'd movement might stress out the dwarf gourami so would I have to move him to my 40 gal community tank with other fish and another male dwarf gourami?