How do I just COPY some photos from the iPhone to the Mac? I don't want to transfer to the Mac I want to have a copy them.

If you are importing with Image Capture and not with Photos, you can disable the checkmark "Delete after Import", see: Transfer images in Image Capture on Mac - Apple Support

"By default, items you download remain on your device. If you prefer to remove them from your device, click the Action button  in the Image Capture toolbar, then either deselect “Keep originals” or select “Delete after import” (the option available depends on the type of device you connected)."

There used to be a similar checkmark in Photos for Mac below the toolbar, when importing from an iPhone or iPad. I cannot check this on my iPhone any longer, because I am using iCloud Photos on the iPhone and then it is not useful to download manually as well.

See: Import photos from a camera or phone using Photos on Mac – Apple Support (UK)

Do one of the following:

• Import all new photos: Click Import All New Items.
• Import a selection of photos: Click the photos you want to import, then click Import Selected.

1. If a message asks whether you want to delete or keep the photos on your camera after they’re imported, click Delete Items to remove the photos, or click Keep Items to keep them on the camera.
2. Photos imports your photos. To cancel importing, click Stop Import.

This should not happen, if "Delete after Import" is disabled, unless you have turned on iCloud Photos and deleted the photos from the Mac.

To get the photos back to the iPhone, you might add them to a Shared Album. This would be the quickest way. Shared Albums do not count against your Cloud Storage, and this way you can browse the photos on the iPhone and other devices. But Shared Albums are scaling the photos down a bit, and some metadata will be stripped.

Or, you could sync the photos back using a USB connection. This will let you sync selected albums to the iPhone. But again, the photos will be down sized a bit and some metadata may be missing.

To get the photos back in a full quality, you could restore the iPhone from a backup you made, before the photos have got deleted. Only then it will be like before: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Or sync Photos on the iPhone and Photos on your Mac with iCloud Photos. This bring all photos from the current Photos Library to the iPhone. To sync only a few albums back, you have to create a second Photos Library with only selected albums and enable iCloud Photos for this smaller library.