I'm not 100% sure about cross-refs remaining intact (though it wouldn't be too much to check). What I like is that editorial changes are quickly made across layouts, you can update and switch out images for the different layouts using the Links panel, and you can have the same styles, but define each layout's version of them differently. It takes a little preparation ahead of time, but if you do it often or if you have lots of pages, it's worth it. Remember you can create the first layout (for instance if you start with the print version), apply all the liquid page rules, then save it as a template. When you're ready to create a new book, open the template and work away, then create the alternate layout when it's done. You really want to make sure you have your first layout as done as you can when you make the alternates. If you were to add something to the original layout afterwards, that item won't appear in the alt layouts...though you can use the Content Collector/Placer tools to add those items in (and still have that connection). Here's a four-part article I wrote on Alternate Layouts...and there are lots of videos on the subject matter as well: https://creativepro.com/understanding-liquid-layouts-part-one/
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