Inheritance law in Taiwan - wills?


I am currently doing research in an inheritance matter and one of my books said, it is not possible to choose someone as their universal sucessor (heir) in a will, only to change the quotas of family members etc. and legacies. Is this correct? And if yes, what is the effect if somebody chooses somebody as their heir in a will - is it invalid or can you “convert” it into a legacy via interpretation?

Thank you for your help!