For me, whatsapp video doesn't work at all. When I use it with my girlfriend (I have iOS, she has a new Android phone) her video has a real bad quality while I can see hers perfectly fine. Voice quality is good as well. Video quality is perfect on Duo and Skype and we're both on WiFi, so that's not the issue.

Don't know if it's due to the geography (across countries in Europe), but I couldn't find a solution yet. Calls work fine as well.

I'd love to get rid of Duo but have to keep using it as I don't want to use Skype on my phone.