From the horses mouth, or at least 1-855-law-guns:
It doesn't matter what angle, if any part of the grip you hold goes below the trigger guard it's not compliant on a featureless rifle in NY. Shops can sell anything they want and have their own interpretations, but that does not make the part legal.
Above are their words not mine.
So, in reality, the only legal options for just a grip are the spur or a fin grip.