Does npx uses yarn?

npx create-react-app executes create-react-app binary, and create-react-app uses yarn to create your project (if yarn is installed). that's why you can see yarn.lock and also why yarn-start works.

Difference between npx create-react-app and yarn create react-app

They both executes create-react-app binary. create-react-app is the one who decides whether it wants to create the project with yarn or not. to use npm in create-react-app, use --use-npm flag (no matter you execute create-react-app with npx or yarn or directly, you should set it if you want it to use npm .):

create-react-app my-project --use-npm

create-react-app uses yarn for the setup if it's installed.

So, if yarn is already installed in your system, then npx create-react-app my-app --template redux and yarn create react-app my-app --template redux would give you the same end-result.

And it is already installed in your system, that's why it has generated yarn.lock and not package.lock.

yarn.lock is generated to keep the exact version of the installed packages.