there are two pieces - Percona Server for MongoDB and Percona Operator for MongoDB.
Percona Server for MongoDB is a 100% compatible alternative to MongoDB Community version. On top of the community version we add various enterprise features and they are 100% free and source available (see feature comparison here).
Percona Operator for MongoDB - it is Percona’s code, not a fork of the MongoDB Operator. We created it from scratch, it is also 100% free, source available and feature rich.
As for production question - both Server and Operator are used in production by lots of community users and customers. There are bunch of case studies on our website.
I’m not sure I understand the diffs question. What was compared to what?