Hello,
In your case I would recommend you to create staging site (full copy of the existing one) and update theme there first. Then if everything is ok you’ll be able to update production site. If not then you’ll have a time to fix the issues and only when everything will be fixed update production. If you want we could help you with this but we need WP Dashboard and FTP access to your staging site and link to production.
You may try to enable both builders at the same time but we can’t guarantee that there are not any compatibility issues between them.
Regards