To me, your primary house determines your alignment, that is which house you actually belong to. Your secondary house determines your mindset. If both houses are the same, that means you're a true Gryffindor/Hufflepuff/Ravenclaw/Slytherin.
For example, Gryffindor + Hufflepuff = You're a Gryffindor with a Hufflepuff mindset
To me, your primary house determines your alignment, that is which house you actually belong to. Your secondary house determines your mindset. If both houses are the same, that means you're a true Gryffindor/Hufflepuff/Ravenclaw/Slytherin.
For example, Gryffindor + Hufflepuff = You're a Gryffindor with a Hufflepuff mindset
Edited by kkj12345