Cancellation Policy tips and Listing on other OTAs

Hi All,

I have my Airbnb listing set to "Firm (New)" for cancellation policies. Wanted to know what your guys' / gals' thoughts are on what is the best cancellation policies out there? 

Also, I have my STR on Airbnb and VRBO. Should I put it on Bookings.com too? What other OTAs are worth listing on? Is it even worth it to list on others other than Airbnb and VRBO?

Thanks in advance all!

-Gulliver