I assume what follows is principally about Terza (third).
The right elbow should be waist high (real waist, not hips) and inline with the right knee and foot. The left is tucked in a bit.
When striking, the left arm needs to be extended to form a straight line with the right. And yet, he rarely does this in the plates.
The right arm should be straight and inline with the sword. The plates do demonstrate this. Again, it should be at waist height so that it divides the body equally top to bottom and side to side. Note that ‘bottom’ in this context is the knee, you are looking for the midpoint of the target areas of the body.
Always aim at the right breast or thigh, whichever is more uncovered. Don’t aim for the left-side no matter how well presented, it’s a trap. The time and distance needed to hit them are always far longer than what’s needed to remove them from danger.
Don’t tuck in your sword arm, it will weaken your defense and slow your offense. This is especially problematic in the measure of the increased foot, where you want that quick tempo. And on longer attacks the body’s power is completely expended before the arm reaches full length, thus not allowing the energy to transfer into the sword.
Don’t extend your sword arm outright either. It won’t be in the right place to defend you nor can if offer momentum to your attack.