As far as I know, when a solution is imported into CRM, it will overwrite anything on the system with what's in that solution whether it's managed or unmanaged. So if you import an unmanaged solution which contains, let's say, entity A, a web resource for
entity A and a process for entity A - these will be written to the default solution.
If you then import a managed solution containing entity A, the same web resource as above and also 2 different processes for entity A, these will then be imported into CRM but not replace the default solution. So if you were accessing entity A, you'd see
the form, attributes, etc from the managed solution, the web resource from the managed solution and 3 processes; 2 from the managed solution and 1 from the unmanaged solution.
Delete the managed solution and it will revert to the default solution where it would start to use entity A, etc from the unmanaged solution.
Nevertheless, it's always a good idea to take a back up of the components before you start in case you need to revert back.
