As was said above, aim for a focal ratio around 5x the pixel size of the camera. However, also be aware that barlows don't usually have a fixed "magnification" when it comes to imaging. This is explained well in the Teleview website here - you may well be better off with a 3x barlow (much more common that 4x).
https://www.televue.com/engine/TV3b_...=52&Tab=_photo
To get the correct colours for the planets, you need an IR cut filter, I just use the ZWO one on my 224 which just screws into the camera nosepiece.
https://www.bintel.com.au/product/zw...v=322b26af01d5
The 16" Dob should be a real planet killer, if you get some good seeing you should expect excellent results. As well as Christophe's book, have a look at these tutorial videos, I find them to be very helpful.
http://planetaryimagingtutorials.com/
Andrew