An interesting video by Dave Durante where he explains his take on a proper handstand form.
Dave begins the handstand with slightly bent arms and knees bent at 90 degrees, which should represent the worst handstand form.
Instead, the feet should be together with arms and knees locked out, which really is a classic curved handstand. It’s worth mentioning that Dave consider this form to be less stable than a straight handstand, which is debatable and depends on other factors. To go from the curved to the straight handstand, press your toes up, open up the shoulders and find your “sweet spot” for balancing.
Going from the first handstand position, to the curved handstand and finally to the straight handstand does require a lot of practice, so it’s definitely not for beginners.