V1 and V2 both use the same SDK package. The difference is with how you initialize it:

const BitGoJS = require('bitgo');

// Read the user authentication section to get your API access token

const bitgo = new BitGoJS.BitGo({ env: 'test', accessToken: process.env.ACCESS_TOKEN });

var coin = bitgo.coin('tbtc');

if you initialize the coin as shown in the last line above, it will use v2. If you do not initialize the coin and use the bitgo object just like in our v1 docs, it is v1.