Sounds like you are on the right path. If you delete the filebeat-* index pattern then run filebeat setup --dashboards -e this will recreate the index pattern using the fields from that version of filebeat.
If you have old data whose types conflict then you'll see this in Kibana when you view the index pattern. If you care to migrate the old data to the new schema then you can reindex. If you filter on the conflict fields then if you click on an individual field it will show you what indices contain the conflict. This can help guide your reindexing efforts.
From 6.x to 7.0 there were breaking changes in the field names. https://www.elastic.co/guide/en/beats/libbeat/7.9/breaking-changes-7.0.html