It depends on where you want to teach. 4 week courses are the best because you usually get 6 hours of teaching non-native speakers. Some employers are looking for that number. If you take a blended course, you usually get less hours of teaching non-native speakers. Bottom line, if you can do a 4 week course, that's best. The next best would be a blended course and last would be an online course. I've looked up Bridge Linguatec and they seem to be accredited through ACCET.