Vivaldi Webmail access and settings
I see two different ways to access my vivaldi webmail. Has one superceded the other? I found this one first https://webmail.vivaldi.net/ but found it awkward and settings very limited. This one seems to be better: https://mail.vivaldi.net/webmail/ I did not see any help screens for clarification - most is evident anyway on the second url.
The first link shows the improved version, the second one is the old one. It's just interface differences and a work in progress. And I don't know how you found one first and the other later, because both can be accessed with the mail button on top of this page.
As a user, at this point, I would stick to the old one. There are very few settings in the improved one and it was confusing to work with.