Checkbox

A single boolean opt-in, submitted with a form. For a setting that applies instantly use Switch.

Checkbox means staged: the change lands on Save. Switch means instant. Never mix the two in one group.
Wrap it in a <label className="o-choice"> so the whole row is the hit target.
Use indeterminate for a parent whose children are partly selected — never as a third user-settable state.
A trust checkbox that a jurisdiction requires blocks submit, and the copy says so.