Importing contacts and emails to a new account does not mean you will loose them from your original one, it is simply a method of transferring them to your new account. Once the import is complete, it is up to you if you want to delete your old account or not, as you will already have the emails and contacts in your new one.
I hope this was useful! Please let me know if you have any other questions about the process.
There is currently not an option available to select the emails you want to import from your old account, I´m very sorry for the inconveniences this may cause!
What I would recommend you to do is to create a new label and put in all the emails from 2016 onwards that you do not want to have in your new account, proceed to import all your emails to your new account and then eliminate this label from your new account so that you only have the ones you want.