Photo size when transferring from iphone to PC/Mac

There are many ways to transfer photos from an iphone to a PC or Mac and many web pages explaining how to do this. However, I haven't found one that addresses this question...

If my iphone is set to "Optimise iPhone Storage" and, because there isn't much spare space on my iphone, the photos on the iphone have been compressed, will the photos that are transferred to the PC/Mac be the compressed ones on the iphone or the original, uncompressed ones stored in iCloud? If the latter, then presumably the iphone knows to download the originals from iCloud before transferring them, but what if the iphone is off-line at the time of the (attempted) transfer?

And is the answer the same, regardless of the method by which I get the photos from the iphone to the PC/Mac?

Thanks in advance.

PS : I would simply test this, obviously, but my iphone currently has lots of space. I'm trying to work out a system for sharing photos among a wide group of people that ensures the "recipient" always gets the original, high quality photos from everybody.