What happens to the edits performed on an iOS device when importing to Photos on a Mac ? Looks like they are kind of lost...

How are you moving them to your OSX device?

There are "sidecar" files for each edited JPEG with an .aae extension. the edits are in there. If present in the same folder as the JPEG, OSX Photos will "respect" the edits and actually allow to revert to original.

Those .aae files are not sent in a Photo Stream as there is no app to interpret them. Photos with edits would be flattened before sending.

To transfer the edited version with my Photo Stream, save a duplicate of the edited photo to the camera roll.

Then the edited version will be transferred by My Photo Stream.

The easiest way to transfer edits in a lossless way between your devices is iCloud Photo Library. All edits will sync between your devices.

ahhh... so the thumb is flattened, but if you import or make a copy, you get the original with sidecar file? Good to know. Thanks.

Then those edits should have been imported at that time. In Photos, if you "edit" one of your imported photos... do you not see your edits? Is there an option to "revert to original"?