I had an account YEARS ago, but couldn’t remember which email address I used back then. So, I tried one, then another, and finally found the right one. Now, however, I have 3 accounts. Only one has a subscription. How do I remove the inactive ones?
Also, I never did figure out which email address I originally had and I am hoping I can find it to get access to my OOLLDD toons (like WotLK era). How can I start with that?
Thank you 
You could start here if they are starter accounts, never upgraded.
https://us.battle.net/support/en/help/product/wow/181/878/solution
Not sure if you can remove them otherwise.
Based on Delete a World of Warcraft Question and Answers:
Delete a World of Warcraft Account - Blizzard Support (battle.net)
Answer is:
“It is not possible to delete individual World of Warcraft accounts from your Battle.net account.”
AND
You can delete Starter Edition accounts.
Blizzard Customer Support cannot assist with deleting accounts.
You can use the self-help option the others have linked to remove a Starter Edition license. You have two on this Battle.net account.
Looking at your WoW#1 license you do have a few characters on Ysera that were created back in 2014-20015. I’m not sure if you were referring to those or you may have another WoW license out there.
If you have character names along with class/race, I might be able to take a look, but depending on the age, they can be difficult to search for.
Thank you Vrakthris that was what I was looking for. Ysera sounds like the correct server.