Hi Naiuma,
For Migrating: My first thought is that the ‘Water’ and ‘Landmass’ plugins are not enabled in your new project. (They are disabled by default) - Although Control Rig plugin should be enabled by default, so I’m not sure what to make of that.
For Project size: Go to Project Settings and uncheck ‘Use Pak File’, then you’ll have a better idea of what’s taking up the space. You could then add directories to ‘Directories to never cook’ if you have content that you know should not get packaged.
Cheers.