Rebuilding backend of website

I have a client whose site was built with WP Bakery builder and she would now like to change it to Elementor. This is a live site.
What is the best way to go about this? Should I use a subdomain to recreate all the pages with Elementor and then transfer once it is all ready?

Either that or just create the new pages with Elementor and then delete the old ones, but usually it’s better not to work on a live site.

I find that installing Elementor on a site that has another builder already in use can start bringing up small bugs. So would recommend working on a subdomain in this case.