We need to migrate an old application to Lightning. I was looking at here What is suggested approach to transfer VF pages to be lightning ready I wonder is this still the best approach when migrating from VFP to Lightning? I am trying to figure out best approach for migration. Also with the approach mentioned, do the pages become responsive in nature?
Keep in mind that reskinning the application using
apex:slds is not a permanent fix; it's meant to give you time to migrate your code to Lightning. This means learning the Lightning Component System and the Salesforce Lightning Design System.
I can add on few things from my experience.
Phases: Always have a phased approach - either by app, or by users pertaining to a specific geography. It gives you good time to train the users and get a feedback so that if something goes wrong its easy to fix it in Phase 2.
Custom : If you have implemented by not using much of customization, it would be easy to migrate the standard pages and then the custom pages. For intermittent solution you can use SLDS.
Reusable custom components : Make sure that you have a good amount of discussion with architects and developers to identify re-usable custom components. They might be time consuming, but once they are up and running its plug and play.