So how does placing 12th at NSDA Nationals compare to doing well in math competitions such as scoring high on the AIME or qualifying for USAMO
Why is there any reason to compare? Both are wonderful accomplishments.
You do you. Participate in ECs that are meaningful to you because you enjoy them.
There’s no need, or effective way, to “compare” such things.
A great mathematician and a great debater are both great. We need everyone and every interest. Also, it isn’t the trophy but the story behind it, which is important.