the female will be the larger of the two. if you buy 2 males, one will switch to female and grow larger. the trick is making sure you dont buy 2 females. once theyve gone from male to female they cant switch back.
yep. so long as they are the same species they should be fine.
Ive often wondered how they decide which of the two would turn female. like, when 2 males are together do they talk about it? do they flip a coin? what if they try to switch at the same time? ha.