There's no lock-in here on the desktop version of the browser, even if they were big enough for that strategy to work.
Passwords and bookmarks are freely exportable, and even if they aren't in the future, they can be transferred to another computer or extracted from the profile data without issues.
But they all do this. Passwords and bookmarks that can't be exported or transferred easily are the usual suspects
Vivaldi seemed big, bloated and slow the last time I used it.