Hi D. I'm Greg, an installation specialist and 9 year Windows MVP, here to help you.
If you're sure you've retrieved all of the files you need, still have email access to the account online if needed, and anything else specific to that account then go ahead and delete it.
Since you have the account you want to keep set up and running, and would know if it's missing anything that needs retrieving from the old account, then you should be OK.
This will not delete the MS account online including any email or apps you own in it. To completely delete a MS Account see this guide:
https://www.howtogeek.com/227763/how-to-complet...
I hope this helps. Feel free to ask back any questions and let us know how it goes. I will keep working with you until it's resolved.
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