Hoping you all can help me with a very irritating issue with my catalog sync settings. I currently have ONE collection marked to sync with 1500 images in it, that's all. But, everytime I run the sync it is sync-ing every single photo in my catalog (over 70,000) and maxes out my RAM making my computer unusable. It obviously stops when I turn off sync entirely, but I would really like to be able to access the few things I have assigned to sync when I need them. Currently it's just totally unusable.
Lightroom Classic, on its own, does not sync all your collections (and all your photos) to the cloud. Why do you think LrC is doing this?
Show us (a portion of) the Collection Panel in LrC so we can see that it has synced all collections. Show us a screen capture of something that indicates all of your photos are synched with the cloud. (Use the "Insert Photos" icon to include screen captures in your reply; do not attach files).