Lr Classic will only sync to one single catalog.
Keywords will not sync between Lr CC and Lr Classic. Also, folders created in Lr CC do not sync as Collection Sets in Lr Classic.
Some duplication will occur if using both applications. For example each application stores smart previews differently. If using those for editing you need to be aware that they could look completely different until everything is fully sync'd in both Lr CC and Lr Classic.
Thanks for responding. So I know that Lightroom Classic will only sync to one catalogue and that Lightroom CC will only sync with one catalogue as well, but I'm wondering if I install both applications on another computer, after I've synced my one catalogue between both apps on my main computer, if I open up Lightroom CC on my new computer first, (which will have my catalogue from the first computer as it's catalogue) won't it then want to sync down the Lightroom Classic that I open up on that same new computer? Does that make sense? Thus making my catalogue synced on both computers? Or no? Or am I completely confused? Well, I know that I am, but I'm trying to un-confuse myself. Thanks for any help anyone can offer me in this regard.
That would only work with a shared Lr Classic catalog where the catalog, previews and files are stored on an external hard drive and where the ehd is always available to be connected to either computer.
OK. So that makes sense. If I use Lightroom Classic on a second computer, barring doing the external hard drive option that you just explained, it will not have anything to do with Lightroom CC nor will Lightroom CC have anything to do with it. Essentially, barring your example, the 2nd computer's Lightroom Classic would work just as it does now, with a different catalogue and un-synced.
Thank you. Wish it would allow us to finally work on the same catalogue on separate computers now that our pictures can be stored in the cloud. Kind of dumb that it won't. But thank you for clearing that up for me.