if you delete the thumbnails in People in Photos does it delete the original

I am not sure, which thumbnails you are asking about - the thumbnails for the people albums of each named person, or the thumbnails inside the album of a person corresponding to the individual photos of the person?

• when you delete a thumbnail in the people album of a person, the photo linked to this thumbnail will be moved to Recently Deleted and then later deleted from all devices.
• When you remove the People album of a person from "People", just the person will be hidden, the photos in this people album will remain in your Photos Library.