MongDB is the natural DB to use when using Nodejs for your back-end, although I have also used sequalize and postgres. All have their pros and cons but if your building with JS why not keep it in the family!

While easier tooling/interface with the programming language is nice to have, its not recommended to choose database based on programming languages. You choose based on data you are going to deal with.

I used to think that NodeJS and MongoDB where developed by the same people (because i used to read lot of articles showing how easy is to create an app using that combo). I learned a little bit about MongoDB but the requirements of the project i was doing at that time required me to use a relational database. So i think it really depends on what do you need. Remember to always analyze the problem in paper before writing the actual code, you will save yourself a lot of time by choosing the correct database type for your next backend.

As for now i usually use MariaDB with TypeORM, but again, if the project can use MongoDB i could use it because i really appreciate the flexibility of using a document based database :)

It depends on your application, either SQL or NoSQL will fit. I think not be prefer with nodeJS?

Database type is depending on the requirement and the architecture of the application. You need to decide whether you need to use SQL or NoSQL database based on software architectural requirement. Also, you cannot use SQLite for shared DB environment. Somehow, in most of the cases, MongoDb doing well with the NodeJS platform for complex web application designs.

Almost every nodejs developer have used mongoose. I will go with MongoDB as well. But SQLite is an elegant option for side projects.

Normally i use MongoDB with Mongoose because of rapid development. But it comes with performance overhead. In other hand it breaks flexibility that MongoDB provides.

I would use MongoDb

graphQL fixes everything :D

I have used Mongo as dB that works well with the node ecosystem. Have you checked RethinkDB? That's good too.