The plan based on last week’s meeting of the @forums-governance team is to go with Option 1, i.e. we will attempt to migrate content from the old forums while also using a redirect mechanism to keep existing incoming links functional. This is made possible by the amazing technical work by @cquest which is showcased here.
The initial structure of categories for sub-communities is going to be primarily location-based.
See this answer for a summary of the meeting results.