I want to mention two things.
- Yes, CPUs matter, so just get a bigger VPS and run multiple sidekiq instances for rebaking and image processing, it will go faster
- When your import is totally completed it’s always a good idea to do a backup / restore, it will give you better database performance.
These two together: get a big VPS for the import and when you’re done move it to a smaller production VPS (using backup and restore).
Generally an import will not require you to rebake posts afterwards.