do certain places and/ or quests drop photon drops more than others?
No. Any crate or enemy can drop a Photon Drop.
Sine the chance is the same for every enemy or box, the the higher the amount of enemys and boxes the better, so areas like ruins and mines may produce better results.
The chance is 1/1000, isn't it?
or quests such as maximum attack online?
IIRC, Its 1/512 anything for PD's.
I know its somewhere in that ballpark.