Well, we would not suggest you delete any of them except the .Lock file because you may have created or using the smart previews in Lightroom.
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Only the current catalog .lrcat, and its associated previews.lrdata folder are needed. And backup catalogs of course.
Any lock or journal files should be deleted - they should have been auto deleted when closing the app, if they're still present they will prevent the catalog from opening. They are normally only there when the catalog is open.
You can also delete the Previews folder if you have problems, but it can take a long time to regenerate and you normally don't want to do that.
I rebooted my computer and didn't open LR. There was no Lock or Journal file so everything is working as it should. I deleted the unnecessary files and folders, opened LR and everything works great.
Thanks for the help.
I started this cleanup campaign because LR had become slow at simple operations even though my computer is new and fast. I suspect the biggest culprit was that I hadn't rebooted my computer in a few days or longer. Another potential help is I deleted a few hundred recent photos. I suspect that those two things made more of a difference than deleting the folders on my SSD.