Earlier quoted context omitted.
Only using whatsapp without other facebook accounts should still be fine. Whatsapp has end2end encryption (unlike FB messenger) and if you don't use other FB products they can't use your data for ads. Obviously not as good as an independent messenger but will cause the same revenue loss for FB.
I believe that’s only text. Try sending someone a video. Takes a while. Try forwarding that video to someone else moments later. Happens pretty quickly. Same applies with photos in my experience. I’d assume voice notes,location pins, etc are also subject to this as well.
If you forward already converted media it will be taken from the gallery in it's compressed, substantially smaller version.