Platies are fine as far as I can tell,swords......well,I had some in the past that were a bit vicious but never really attack any of my fancy guppies------and I assumed that when you mention having 4 gups,you meant fancy ones with flowing tails and all-------Mollies,let's see,I had a trio of gigantic hifin,sailfin mollies and I can tell you that after a week or so,I had to bring them back to the LFS.There was chasing,biting you name it.
My males gups suffered the most being unable to swim as fast as the mollies they ended up with parts of their tails torn and ripped.
But,not all varieties of mollies are aggressive and territorials.It is hard to tell.Remember you may not want some of the bigger varieties since you only have a 10 gall. and they need lots of space.look for sign of agressiveness,see if any is chasing the rest and if they bite at each other.If you see this stay away.Ask anyone that works there,maybe they can help,even people buying fish,most will help you.
Good luck w.your fish.Lets know how it went.