Travel & Leisure mentions that Airbnb may not be a good lodging option since they too are jacking up their rates (and why not, this is SOP when a circus comes to town). They recommend checking these alternate sites - Le Collectionist, HighStay, Sonder and Onefinestay (which is owned by the Accor chain).
The opening ceremony will involve teams sailing down the Seine. All the good spots to watch will require tickets but T&L claims you can still find viewing spots along the esplanade.