I recently attended a board meeting where a formal conflicts of interest policy did not exist. Thanks to a long-standing senior board member reminding everyone that the financially conflicted board members should not vote, at least some semblance of propriety was maintained.
Good governance depends on board members speaking up: about implementing policies; about issues that arise that do not seem right but are not covered by policies; about anything that seems relevant to good governance. Written policies are important, but they are useless if not actively applied. Good governance requires proactive participation at meetings, as well as communication in-between meetings in smaller groups, to monitor implementation of decisions and unexpected issues.