This is the best overview you are likely to see, and it agrees with you: sephardicgenealogy.com/sephardic-dna/

Its... whats the opposite of fun while still being interesting... gripping? tragic? that conversos and their descendants did A LOT to obfuscate lines of descent. part of surname discontinuity through families descended of spanish jews was to insulate family members from each other.

hey that's very helpful