Full size images load at the bottom of a Envira gallery and it really shouldn't.
To make sure the full size images do not load, I need to turn off the Lazy Loading on Jetpack. I don't know any other way.
For mobile browsing, the Lightbox images are very very small and can't be fixed via the additional CSS.
For the above two issues I don't know if it's exclusive to the Lite or i.e. the unpaid version or somehow the issues are fixed on the paid version.