I think that sending emails now would be fine - I've been in touch with a lot of my POI's both before and after submission, and they've all been courteous and willing to help. Don't expect all of them to respond (I'm sure they get a ton of emails this time of year), but even if they just see something from you in their inbox it can only help your application. Many professors even expressed that they appreciated seeing somebody who was willing to actively pursue what they wanted to do in graduate school, so you'll leave a good impression. Just remember to use your professional or university email so your letter doesn't go straight to their junk =)