It's just great to see work on self-hosted cms, and PHP nevertheless, the easiest one to host. Open source has forgotten the art of making the web open to everyone, not just to BigTech employees.
Though it probably depends on your definition of 'narrow'. I'm guessing a lot of Americans think the average SF street is narrow, and it would be a medium or even wide street in some other countries.
Depends on your use case. PostgreSQL is better if you actually USE any of its more advanced features (e.g. PL/pgSQL, JSON support, etc). But if your data model is simple and your need for scale is high, then MySQL is FAR easier to cluster and scale. Especially if you're working with Percona or another MySQL variant.