Welcome to the NotionApps community @pgawd! Filtering based on relations is high on our priority list. You can track and vote for the feature here, List filters with properties from related databases.
As for the bonus part, this is also something we’ve come across before, but have not picked it up as in-app filters are available on relation selection screens to data filter in real-time. It’s an extra step and is not ideal and we will work on improving this in the future.