The most strict TypeScript tsconfig mode

tsconfig.json

{
  "compilerOptions": {
    // Strict Checks
    "alwaysStrict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "useUnknownInCatchVariables": true,
    "strictPropertyInitialization": true,
    "strictFunctionTypes": true,
    "noImplicitThis": true,
    "strictBindCallApply": true,
    "noPropertyAccessFromIndexSignature": true,
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true,
    // Linter Checks
    "noImplicitReturns": true,
    "noImplicitOverride": true,
    "forceConsistentCasingInFileNames": true,
    // https://eslint.org/docs/rules/consistent-return ?
    "noFallthroughCasesInSwitch": true,
    // https://eslint.org/docs/rules/no-fallthrough
    "noUnusedLocals": true,
    // https://eslint.org/docs/rules/no-unused-vars
    "noUnusedParameters": true,
    // https://eslint.org/docs/rules/no-unused-vars#args
    "allowUnreachableCode": false,
    // https://eslint.org/docs/rules/no-unreachable ?
    "allowUnusedLabels": false,
    // https://eslint.org/docs/rules/no-unused-labels
    // Base Strict Checks
    "noImplicitUseStrict": false,
    "suppressExcessPropertyErrors": false,
    "suppressImplicitAnyIndexErrors": false,
    "noStrictGenericChecks": false
  }
}

Thanks a lot, next.js comes with default strict settings. Here are their default tsconfig.json settings:

{
  "compilerOptions": {
    "lib": ["dom", "dom.iterable", "esnext"],
    "allowJs": true,
    "skipLibCheck": true,
    "strict": true,
    "noEmit": true,
    "esModuleInterop": true,
    "module": "esnext",
    "moduleResolution": "bundler",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "jsx": "preserve",
    "incremental": true,
    "plugins": [
      {
        "name": "next"
      }
    ],
    "paths": {
      "@/*": ["./src/*"]
    }
  },
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
  "exclude": ["node_modules"],
}

Since "strict": true includes most of the settings you mentioned, I only had to add these:

{
  "noPropertyAccessFromIndexSignature": true,
  "noUncheckedIndexedAccess": true,
  "exactOptionalPropertyTypes": true,
  "noImplicitReturns": true,
  "noImplicitOverride": true,
  "forceConsistentCasingInFileNames": true,
  "noFallthroughCasesInSwitch": true,
  "noUnusedLocals": true,
  "noUnusedParameters": true,
  "allowUnreachableCode": false,
  "allowUnusedLabels": false
}

forceConsistentCasingInFileNames is true by default since 5.0.