Hey!
Now there is a Lay Theme update available: 1.7.1
You will have a new option in: "Lay Options" → "Misc Options" → "Never show resized versions of your images"
You can try that. That might slow down the loading of the images.
I also added more sizes in my code (2560, 3200, 3840, 4096). So in case you want to keep using the normal way lay theme shows images, now it will also show bigger ones.
For the Lightbox there is now an update 1.2.1 which has a new similar setting:
"Lay Options" -> "Lightbox Addon" -> "Never show resized versions of your images"
Please let me know if that helps! If that doesn't help you can send me a link to your website via chat so I can take a look. Please also send a link to this topic so I know what its about.