You can load labels by accessing the labels property of a term.
import { ILabel, ILabelData, ITerm } from "@pnp/sp-taxonomy";
const term: ITerm = <see terms article for loading term>
// load the terms merged with data
const labelsWithData: (ILabel & ILabelData)[] = await term.labels.get();
// get a label by value
const label: ILabel = term.labels.getByValue("term value");
// get a label merged with data
const label2: ILabel & ILabelData = term.labels.getByValue("term value").get();
Sets this labels as the default for the language
import { ILabel, ILabelData, ITerm } from "@pnp/sp-taxonomy";
const term: ITerm = <see terms article for loading term>
// get a label by value
await term.labels.getByValue("term value").setAsDefaultForLanguage();
Deletes this label
import { ILabel, ILabelData, ITerm } from "@pnp/sp-taxonomy";
const term: ITerm = <see terms article for loading term>
// get a label by value
await term.labels.getByValue("term value").delete();