I've been using WordPress for about ten years now but I've never swapped themes and I did some reading but it isn't clear to me the best way to update a theme while keeping an e-commerce site live. Most of the walk-throughs and guides that I've read so far just say to put the site in maintenance mode but if it's going to take quite a bit of time to migrate everything over how do I keep the site active or is there not a way to do so? Sorry if I don't know all of the proper terms for this because I'm self-taught.
I have several domains parked so I was thinking I could clone the e-commerce site onto an unused parked domain and then work on it over the course of a few weeks and then when I'm done with the new site transfer it to replace the existing e-commerce site. The main issue is that I have around 120 products and I assume that when I swap themes the formatting is going to get either really messed up or I may even have to manually add all of the products because the existing WP Bakery theme is over ten years old.
Working on a clone then merging the changes is probably your best bet.
Test on a staging server (a free and simple way of doing this is to use Local from https://localwp.com). If it goes well, put up a Coming Soon page (eg use the “CMP” plugin) and replicate the changes on the prod site.
However, if your new theme uses a different page builder, then you’re going to need to rebuild any pages built with wpbakery. Typically you wouldn’t build your product and blog posts with a page builder like wpbakery.
And / or you can have different themes by role. You can work on a new theme with your admin account. You need a plugin for this. Of course use a staging copy.
Clone into staging branch then push branch to live once you’re 100% done.