I don't know about those schools, but there are different kinds of EP programs. Typically, about 1/2 of the subjects will be taught in English, hopefully by NES (Native English Speakers). It's not unusual for a school to hire Filipinos, Indians, Danes, Dutch, Nigerians etc., especially to teach Science, Math, Health, etc... personally, I would be wary of schools that have non-NES teachers teaching English as a subject.
Most EP programs have smaller class sizes, usually limited to 25 students for primary and 35 students for secondary. They typically have AC in their classrooms, along with computers/projectors and often the students have tablets or laptops that they can use for various lessons.
Pay a visit to the schools if you can, in addition to asking about the things I mentioned above, find out how well the people in Administration can speak English. If they cannot speak English, how do they communicate with the teachers? Do they just issue occasional badly worded directives and then complain when the foreign teachers don't understand or comply? Or do they have at least one or two staff members who speak English well?
Also ask about faculty turnover. Do most teachers stay for at least 3 or 4 years, or do they have a majority of new teachers every year. Without some continuity in the faculty, the teachers cannot really teach effectively.