I am similar to the other response. I only sent out emails to the PIs that were especially interesting to me and with whom I wanted to speak. I did this mainly with the schools that were my top priority. The responses from PIs were nice and usually amounted to "Thanks for the interest. If you get an interview, we will be in touch." This made me decide it was best to wait until after interview invitations to send out more emails. It doesn't seem like reaching out the professors beforehand greatly impacts your application. It has the possibility of giving you a leg up, but there's no guarantee. It seems that experience in the field is normally prioritized, and reaching out to professors is ancillary unless otherwise stated by the program. If you didn't reach out to many professors, I wouldn't worry. Good luck, and I wish you the best!