The order of your attendants can be anything you want, by height, by color of hair, by age, who has the best tan, it really doesn’t matter. But, if you have spouses who are in you bridal party, it is good to pair them up together. And if there are strangers in the group, be sure to introduce them to each other before you line them up.
Entering two by two, or unescorted is really just the couple’s preference. There is no set rule on this, it is a six of one, half a dozen of the other kind of thing. Some people think it is more elegant if the men escort the bridesmaids, but again, it really doesn’t matter.