Cycling with Platys/mollies?

[FRIENDLYFISHIES]

Are platys or mollies a hardy fish for a fish in cycle?
I plan to turn the tank brackish then add my 2 male guppies (who are currently already brackish)...but then I realized most fish they sell in stores are fresh water and will need to be acclimated to brackish slowly over the course of a couple weeks (to be safe)...Im thinking if I plan to add additional fish asside from my guppies I should probably do it now so they can get used to the salinity over the 2 weeks that im taking to raise it, does this make sense?

A few other Q's will include-
Which would be the more suitable tankmates; guppys + mollies or guppies + platys?

Im going to do my best to get all males...not sure what my luck with be, ive heard guppies will cross with mollies??
Will they also cross the platys?
If they are all males and no females im assuming they will get along alright?
Im also wondering, some Mollies get pretty big, will they make a snack of my guppies??
Ive become quite attatched my 2 male guppies, I really hope to keep them around a while and dont want to introduce any fishes that plan to make a snack of them lol.

Thoughts/advice/suggestions?

[mousey]

I would recommend a fishless cycle.
All livebearers seem to go together in my experience. it is purported that some will interbreed but that has never happened to me in all the years I have kept them.

My mollies leave the guppies alone- no snacking!
Once you get your tank cycled gradually turn it brackish if that is what you want-- but none of those fish really need it.
Livebearers are easy to sex so I don't know why you are wondering if you can get all the same sex.
males can become a bit territorial and 'display' a lot if there are no females in the tank.9 Too many hormones)