Actually, first of all, what does it mean to “submit games earlier? Judgment starts immediately, and the sooner the game is sent, the longer its judgment will last? Or just more people will play it, and when the judgment opens at the end of the jam, they will know what to write in the review?

Aaaand secondly: will there be any other themes besides “no words” before the jam starts? I would really like it to be...

 Do you mean sign language? That would work as long as you're not using a font to write it. 

The rating period begins after the submission period ends. Uploads are locked during this time. 

It's better to submit an entry early before the deadline, even as a placeholder so that you aren't rushing to make it before time runs out.