Bean bag size and type (1 Viewer)

I would like to buy or self build a bag for a trip to Kruger Park. The bag would be used mostly on a car window
I will use Nikon D3100 + one out of

Sigma 150-500 f/5.6-6.3 con attacco Nikon F
Nikon af-s 70-300 VR 4.5-5.6 G
(less likely Sigma or Tamron 100-400)

Which type of bean bag will I need?
I will also use a Canon Powershot SX 60 HS. Would a bean bag be of any use also for a light camera like the Powershot?
I noticed there are different shapes and sizes, and some complain about very big bean bags because they say they make sense only for very big lenses
Very likely I will buy one the bags of this amazon seller:
https://www.amazon.it/s?k=wildlifephotographyshop&ref=bl_dp_s_web_0

I have this one

https://www.ebay.co.uk/itm/Grippa-CAMERA-Bean-Bag-WATERPROOF-material-Size-22cmx22cm-approx-Empty/112043541624?epid=1230209620&hash=item1a1650c478:g:-owAAOSwLdNZvCTP

Thanks
I have been told to get a "C" or "H" bag type, best to be used in cars