No quiz is gonna give you the full answer. At best, a good one can help point you in the right direction. Most are surface-level, generic stuff that fits with any kind of soul-level connection, so they can’t tell you the difference between soulmates and twin flames. You could use a TF birth chart if you wanted something more specific to you and your connection.
Other than that, your own intuition.
Soulmates complement you, fill your gaps, feel like smooth understanding. Twin flames get you too, but they also trigger deep discomfort that forces growth. The runner/chaser dynamic is classic twin flame. One bolts from the intensity, the other chases. Soulmates have rough patches, but not that extreme push-pull.
Synchronicities too. Not just shared tastes, but wild stuff like constant 11:11, parallel life stories, finishing sentences day one. The universe screams with twin flames. Soulmate bonds are peaceful and lasting. Twin flames are turbulent, may not last as a relationship, but the connection lingers.
Think about these and see what fits.