Is it possible to allow users to sign via EchoSign?

Client will then agree to the terms and conditions via Echo-Sign Integration by signing.

Yes, we have this as a widget. 

https://widgets.jotform.com/widget/adobe_dc_esign_services

To add a widget to your form, simply follow the steps from this guide: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-your-Form.