Wow, you've got a lot of different password managers installed. Impressive, as much as confusing. 😉
The topic of this old thread relates to the Vivaldi browser app cooperating with Android Autofill Service when a password manager is installed. This used to be an issue.
I don't think that Vivaldi installs itself as an Android Autofill Service (yet). And I'm not certain that Vivaldi has aims to do so in the future as this may be quite a different ball game.
Like any other browser, Vivaldi is capable of storing passwords in a protected manner and autofill these as the occasion occurs on a webpage one visits. It does not provide this autofill service beyond the browser, such as other Android apps or the Android system itself.