How do I remove/delete the entire "People" portion of the photo library?

What do you want to achieve by disabling the People feature? You will not save any storage, if you delete the albums of recognised people from the People album. You will just prevent these people to be used for the creation of Memories.

• Open thePeople album in Photos.
• Select each Person in the album in turn, ctrl-click or right-click the person and use the command "Remove this person".
• Leave just one person in the album.

It is not possible to disable the People feature. It is a built-in feature that Photos will scan all photos for faces, recognise people, and use this results to recognise scenes and create memories. You can just refrain from naming any people. And remove all detected people but one album from the People album. At least one album should remain, or Photos will reset the face recognition and start over and waste even time on this. You could also simply merge all people albums into one single album and Photos will not be able to learn the faces of single people. Call the merged person "average person" or similar.

Then removing the album with the mixed people will not suffice.

I would try the following: select all faces in the mixed album and drag them to a new standard album in the sidebar of photos, so you can easily find back to the photos where the faces need fixing.

Open again the people album of the mixed person and reject all named faces inside with the command "This is not".

Now use the album with the saved photos to name all faces again, but do not use the same names from the Contacts for the wo people as before, or Photos may immediately merge them again. Use new nicknames that you never have used with Photos. See this user tip: How to Correct Merged People Albums - Apple Community

I have two people photos mixed up (4000 photos)

how can I start over? I would like to remove the mixed “people” and recreate it