If the trade-offs here feel similar to the trade-offs between relational databases and no-sql databases, it's because they are. At the end of the day, all of these technologies are built on top of the same well studied data structures and the innovation is happening by applying them to new industries.
No real sync exists like you mention exists.
The closest solution is what I and a few others do. Using a cloud replication service, such as Micorosft OneDrive, Google Drive, Dropbox....
You put the catalog, all pictures, and make sure to include preferences and plugins in the same base folder, in the replication service. Now, everything will be replicated between the computers. However, and this is a big one, you CANNOT open Lr on the second computer until replication has finished between both computers. Otherwise, your catalog can become corrupted and/or end up with duplicate conflicts.