Besides any housing and possibly gil over the limit, you should not lose anything from transferring to another server. The stuff in your armoire will carry over.

"Rehire any retainers carried over from version 1.0" only concerns characters which were played back in the 1.0 incarnation of this game, and lets you rehire old retainers. Since I am not one of those who played back in 1.0 I am afraid I do not know more than that about this option.

You get 2 retainers for free, and can pay for more up to a maximum of 8 retainers.