What's the difference?

Different Ways of using presets?

I've seen 3 different ways loaders are used, and I'm not sure what the the heck the difference is, 
or which ones are even necessary. 

//#######  In .babelrc file
{
  "presets": ["@babel/preset-env", "@babel/preset-react"]
}

//#######  In package.json file
"babel": {
    "presets": [
      "@babel/preset-env",
      "@babel/preset-react",
    ]
  }
  
//#######  In Webpack config loaders
....
  module: {
    rules: [
      {
        {
          test: /\.js$/,
          exclude: /(node_modules\/(?!(@myfiles)\/).*|bower_components)/,
          use: [
            {
              loader: 'babel-loader',
              options: {
                presets: ['@babel/preset-env', '@babel/preset-react'],
                retainLines: true
              }
            }
          ]
        },
      }
    ]
  }
....

/##########################

One thing I found is that if I omit the the preset definitions in my webpack config then I 
get errors with uglifyjs and other random things. When do you need each? Which are redundant? 

Only use .babelrc. babel will find it and supersedes the use of webpack.config.js . I don't know of any use in package.json.

{
"plugins": [
"react-hot-loader/babel",
"transform-decorators-legacy",
"transform-object-assign",
"transform-object-rest-spread",
"transform-class-properties",
"transform-flow-strip-types"
],
"presets": ["es2015", "react"]
}

When I omit line 29, and don't have a preset definition in my webpack config, I get errors trying to build wepback. One of them was regarding uglifyjs like: SyntaxError: Unexpected token: name (xxxxxx) from Uglify plugin

I dont know the @babel tag does at the front, but this is how we with out @babel tag.
Also never use any configuration in package.json file.

{
  presets: ['react', 'stage-0'],
    env: {
        test: {
            plugins: [
                "transform-es2015-modules-commonjs", //for class inheritance transpiled correctly
                "transform-es2015-parameters",  //for class inheritance transpiled correctly
                "transform-es2015-destructuring"  //for class inheritance transpiled correctly
                ]
        }
    }
}

 module: {
        rules: [
            {
                test: /\.js$/,
                exclude: function (modulePath) {
                    return /node_modules/.test(modulePath) &&
                        !/node_modules\\validate/.test(modulePath); //validate module needs to be transpiled
                },
                use: [
                    {
                        loader: 'babel-loader',
                        query: {
                            presets: ['env', 'react', 'stage-0'],
                            plugins: [
                                "transform-es2015-modules-commonjs", //for class inheritance transpiled correctly
                                "transform-es2015-parameters",  //for class inheritance transpiled correctly
                                "transform-es2015-destructuring"  //for class inheritance transpiled correctly
                            ]
                        }
                    }
                ]

            },

here is the version of babel in use at the moment for me

"devDependencies": {
    "babel": "^6.23.0",
    "babel-core": "^6.26.0",
    "babel-eslint": "^8.2.2",
    "babel-jest": "^21.0.0",
    "babel-loader": "^7.1.2",
    "babel-plugin-transform-es2015-destructuring": "^6.23.0",
    "babel-plugin-transform-es2015-modules-commonjs": "^6.26.0",
    "babel-plugin-transform-es2015-parameters": "^6.24.1",
    "babel-preset-env": "^1.6.1",
    "babel-preset-react": "^6.24.1",
    "babel-preset-stage-0": "^6.24.1",
    "babel-runtime": "^6.6.1",
    "css-loader": "^0.28.7",