I know Nintex Form offers a cool user interface helping people to design better UI form and link to Nintex Workflow. Similarly out-of-the-box SharePoint form can work well with Nintex Workflow. I'm not sure if a custom form (built on Office 365 with JSLink, client-side rendering..) can connect to work with Nintex Workflow.
Your recommendation would be very much appreciated.
The forms will work with Nintex workflow, but Nintex forms offers further integration.
All forms work from Content Types so the tool that is used to create those forms doesn't matter.
You could also use InfoPath forms.
I'm not sure what you mean by connect to work with Nintex Workflow, but I'm assuming that you are asking if we can use Nintex Workflow independently of Nintex Form.
In this case, building a custom form to display your list items should not affect Nintex Workflow as Nintex Workflow mostly relies on connecting to the list item and not the form used to display the list item.
For complex scenarios we have also created custom forms to present the list items, and continued to use Nintex workflow to automate the business process once the data is submitted.
Thank you Ryan and John for your recommendation. Yes I'm a bit worry about using Nintex Workflow independently of Nintex Form. Nintex Form sometimes does not really provide me a perfect form (from UI perspective, accurate at pieces of pixel I would say). Custom form with client-side rendering technologies would be better.