Pros and cons of using aws sdk vs node-fetch

I have a Custom Mutation on my GraphQL schema that looks like this.

type Mutation {
     addSpot(name: String!): String! @function(name: "saveSpot-${env}")
}

Which calls my lambda function generated with the amplify CLI.

My goal here is to put my Business logic in this Lambda function for checking and creating / updating records on my DynamoDB database and sometimes using S3 too.

Since this is done in the index.js, I'm using JavaScript and to specify, using it with ES5.

In this configuration which is: Flutter, AWS Amplify, GraphQL API, DynamoDB, S3 and Cognito, which would be the prefered library to serve my purpose?

I have crossed this options:

1. AWS-SDK
2. Node-fetch
3. AWS-Amplify

Plus, where would I check for permissions to use the lambda?

Best regards