Issue 1:
With these settings in browserlist build failed:

>= 1%

or

>= 2.5%

but works with

>= 1.1%

or

>= 2.5%
ie 11

which both differs only for ie 11

error:

ERROR in ./src/containers/Employees/EditEmployeeContainer.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
TypeError: C:\Projects\topcase\hrketing\src\Web\WebSPA\src\containers\Employees\EditEmployeeContainer.js: Duplicate declaration "modifiedAlternativeNames" (This is an error on an internal node. Probably an
at File.buildCodeFrameError (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\core\lib\transformation\file\file.js:250:12)
at Scope.checkBlockScopedCollisions (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:419:22)
at Scope.registerBinding (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:579:16)
at Scope.registerDeclaration (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:521:14)
at Object.BlockScoped (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:250:12)
at Object.newFn (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\visitors.js:216:17)
at NodePath._call (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:55:20)
at NodePath.call (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:38:14)
at NodePath.visit (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:92:31)
at TraversalContext.visitQueue (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\context.js:112:16)
@ ./src/containers/Router.js 28:54-97
@ ./src/containers/App.js 22:0-73 155:24-35 156:27-38 200:54-65 207:42-48
@ ./src/containers/Root.js 21:36-51
@ ./src/index.js 26:0-37 51:38-42

ERROR in ./src/containers/Trips/CreateEditTripContainer.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
TypeError: C:\Projects\topcase\hrketing\src\Web\WebSPA\src\containers\Trips\CreateEditTripContainer.js: Duplicate declaration "origin" (This is an error on an internal node. Probably an internal error.)
at File.buildCodeFrameError (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\core\lib\transformation\file\file.js:250:12)
at Scope.checkBlockScopedCollisions (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:419:22)
at Scope.registerBinding (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:579:16)
at Scope.registerDeclaration (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:521:14)
at Object.BlockScoped (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\scope\index.js:250:12)
at Object.newFn (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\visitors.js:216:17)
at NodePath._call (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:55:20)
at NodePath.call (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:38:14)
at NodePath.visit (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\path\context.js:92:31)
at TraversalContext.visitQueue (C:\Projects\topcase\hrketing\src\Web\WebSPA\node_modules\@babel\traverse\lib\context.js:112:16)
@ ./src/containers/Router.js 25:56-97
@ ./src/containers/App.js 22:0-73 155:24-35 156:27-38 200:54-65 207:42-48
@ ./src/containers/Root.js 21:36-51
@ ./src/index.js 26:0-37 51:38-42

system:

λ npx envinfo --preset babel

System:
OS: Windows 10 10.0.19041
Binaries:
Node: 12.18.4 - C:\Program Files\nodejs\node.EXE
Yarn: 1.22.5 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.14.8 - C:\Program Files\nodejs\npm.CMD
npmPackages:
@babel/cli: ^7.12.1 => 7.12.1
@babel/core: ^7.12.3 => 7.12.3
@babel/eslint-parser: ^7.12.1 => 7.12.1
@babel/eslint-plugin: ^7.12.1 => 7.12.1
@babel/plugin-proposal-class-properties: ^7.12.1 => 7.12.1
@babel/plugin-proposal-decorators: ^7.12.1 => 7.12.1
@babel/plugin-proposal-do-expressions: ^7.12.1 => 7.12.1
@babel/plugin-proposal-export-default-from: ^7.12.1 => 7.12.1
@babel/plugin-proposal-export-namespace-from: ^7.12.1 => 7.12.1
@babel/plugin-proposal-function-bind: ^7.12.1 => 7.12.1
@babel/plugin-proposal-function-sent: ^7.12.1 => 7.12.1
@babel/plugin-proposal-json-strings: ^7.12.1 => 7.12.1
@babel/plugin-proposal-logical-assignment-operators: ^7.12.1 => 7.12.1
@babel/plugin-proposal-nullish-coalescing-operator: ^7.12.1 => 7.12.1
@babel/plugin-proposal-numeric-separator: ^7.12.1 => 7.12.5
@babel/plugin-proposal-optional-chaining: ^7.12.1 => 7.12.1
@babel/plugin-proposal-pipeline-operator: ^7.12.1 => 7.12.1
@babel/plugin-proposal-throw-expressions: ^7.12.1 => 7.12.1
@babel/plugin-syntax-dynamic-import: ^7.8.3 => 7.8.3
@babel/plugin-syntax-import-meta: ^7.10.4 => 7.10.4
@babel/plugin-transform-flow-strip-types: ^7.12.1 => 7.12.1
@babel/preset-env: ^7.12.1 => 7.12.1
@babel/preset-flow: ^7.12.1 => 7.12.1
@babel/preset-react: ^7.12.1 => 7.12.5
@babel/register: ^7.12.1 => 7.12.1
babel-jest: ^26.6.1 => 26.6.3
babel-loader: ^8.1.0 => 8.1.0
babel-plugin-import: ^1.13.1 => 1.13.1
babel-plugin-macros: ^2.8.0 => 2.8.0
babel-plugin-module-resolver: ^4.0.0 => 4.0.0
babel-plugin-react-intl: ^8.2.10 => 8.2.13
babel-plugin-styled-components: ^1.11.1 => 1.11.1
babel-plugin-transform-react-remove-prop-types: ^0.4.24 => 0.4.24
eslint: ^7.12.1 => 7.12.1
eslint-import-resolver-babel-module: ^5.2.0 => 5.2.0
jest: ^26.6.1 => 26.6.3
webpack: ^5.4.0 => 5.4.0

Issue 2:
I did not check the specs on the scopes, but I am assuming that v8 behavior is correct and that in for (let a of/in b) part b should be outside of the for scope. This is how v8 does things. This is also how babel does things in for of blocks.

"use strict";
var a = [[], [1, 2, 3]];
var i = 1;
for (let i in a[i]) {
console.log(i);
}

is translated to

"use strict";
var a = [[], [1, 2, 3]];
var i = 1;
for (var _i in a[_i]) {
console.log(_i);
}

when it should be translated to

"use strict";
var a = [[], [1, 2, 3]];
var i = 1;
for (var _i in a[i]) {
console.log(_i);
}

A similar (or the same) issue:

"use strict";
{
let i = [1, 2, 3];
}
for (let i in i) {
console.log(i);
}

should have the same variable renames (not the same code) as in

"use strict";
{
let i = [1, 2, 3];
}
var i;
for (let i in i) {
console.log(i);
}

but no variables are renamed in the first variant.