If you are already using web3.js or ethers.js, and do not require functionality such as creating subdomains, transferring ownership, or updating resolvers, use built in ENS features of these libraries.
If you are using React and only need to do forward and reverse resolution of ENS names with built in UI, use react-ens-address.
If you want to have ENS instance deployed into your dev environment, you may want to use embark.io or waffle.io which allows you to configure/deploy ENS registry in your Ethereum test instance.
Otherwise, use ensjs.
Accessing smart contracts directly
All the ENS smart contracts are published as @ensdomains/ens-contractsnpm module.
This is how you include abi into your frontend code.
} from '@ensdomains/ens-contracts'`
This is how you import our smartcontract within Solidity.