I would emphasize the importance of limiting the ::ng-deep to only children of a component by requiring the parent to be an encapsulated css class.
For this to work it's important to use the ::ng-deep after the parent, not before otherwise it would apply to all the classes with the same name the moment the component is loaded.
Using the :host keyword before ::ng-deep will handle this automatically:
:host ::ng-deep .mat-checkbox-layout
Alternatively you can achieve the same behavior by adding a component scoped CSS class before the ::ng-deep keyword:
.my-component ::ng-deep .mat-checkbox-layout {
background-color: aqua;
}
Component template:
<h1 class="my-component">
<mat-checkbox ....></mat-checkbox>
</h1>
Resulting (Angular generated) css will then include the uniquely generated name and apply only to its own component instance:
.my-component[_ngcontent-c1] .mat-checkbox-layout {
background-color: aqua;
}