Generally, for tax credits, you look at where a person is resident, and that's generally a factual determination as opposed to a pure choice. In certain cases, for payments of interest, dividends, and royalties from a source country, there is a cap on what the source country can tax at, and then you would get credit for that. However, if effectively it's a foreign tax credit, you would only give a credit up to and not exceeding what your own tax was. If the rate is 10% in Canada and 5% in Taiwan, and Taiwan is the residence country and is granting a foreign tax credit, it would only give a tax credit up to that 5%. It's not going to have to reimburse more Canadian tax.
In the reverse situation, if Canada is the residence and 5% tax was paid in Taiwan, assuming there's no cap on what we can tax, Canada would only give a credit of 5%.