CAIS is traditional Alberta syllabus and not IB, very different from other international schools like ESF/ CDNIS. They are teaching traditional Chinese and most teachers are caring. Tier II private local - very depend what kind of school it is.
If you are aim to go abroad right after primary, then better study in local school first to establish a stronger ground. going aboard at younger age can adapt to the environment easily.
However if going in a later time such as senior high, then better study in international school so easier to get adapt to the foreign environment.