Public school vs private school requirements

Hi there, I’m new here and I am considering teaching English in Taiwan. I’m from New Zealand (Caucasion native English speaker) and have a B Ed Teaching degree which is a 3 year degree (we don’t have 4 year teaching degrees here - unless it is a Master)… I was wondering if that qualifies me to work in a public school in Taiwan? Also I’m not sure what a ‘teaching license’ is - is that a Taiwan license?? We don’t have teaching “licenses” in NZ. I am also considering doing a TEFL or CELTA course before I head over - is that necessary? I have had a little bit of teaching experience (and child care) and am about to start doing 1-2 days a week teaching here to gain some more current experience. Also, what is the teaching like in a public school as opposed to a private school? Do you have some freedom to create and develop lesson plans based on assessment observations of the students? Or are the lesson progressions largely dictated from textbooks in a regimented way?