The totem stays in your pack.
Dbl click and it is instant change. When in costume you can go into reaper form. It uses last object macro so, I would think it can be dropped in a macro in EC.
Seems to move at run speed when running but the animation is walk so it looks slower but I can not tell if it is slower than run.
Can't mount while in costume. If used while mounted you dismount and go into costume. Have to remove costume before you can mount.
Can polymorph while in form.
Can cast and use weapons as normal while in costume.
So not sure about Ninjitsu speed. But just use macro and can change as fast as your fingers can click.