I am running Lr on two computers. The image files are stored on a shared network drive. Each copy of Lr has its own catalog. Lightroom on my laptop is configured to always write sidecar XMP files. Lr on my desktop is not configured to write sidecar files. I have converted all my raw files to dng. My understanding is that now that my files are in dng format, the Lr “develop” setting are written into the dng files (and in the case of work done on my laptop, the associated sidecar file). Forget about jpg, tif, and psd files. I am only interested is how the two copies of Lr interact with the dng files on my network drive. I have read Martin Evening’s Lr 4 book over and over concerning metadata “develop” data, in particular, his section concerning “Where is the truth?”. Reading Martin’s book, I am tempted to believe that the Lr catalog “develop” metadata on each computer will be selected despite the fact the “develop” metadata was changed (both in the dng file and, if the changes were made on my laptop, the sidecar file) by the other computer. Is that correct? Or, if I make changes to the image on one computer, will Lr alert me to the changes on the other computer? If it does alert me to the changes, can I disregard the update and keep different “develop” settings of the same image file based on the differences between the Lr catalogs on each machine?
For the changes you make on the laptop to make it to the desktop, you'll need to tell LR on the desktop machine to read the metadata from those images. Yes, you'll be given a warning that the image metadata doesn't match the catalogue metadata.
That said, I wouldn't do it that way. There are just too many ways that you can mess yourself up. Two catalogues for one set of images is one catalogue too many.
A much simpler, more bulletproof scheme would be to have both your catalogue and images on an external drive and plug it into the machine you want to do your work on. Or keep your images on the network and just have the catalogue on the external. Or pass the catalogue to the machine where you want to do your work.