You won't need 16GB of RAM. 8GB is even plenty of RAM for Photo editing. I can have several photo programs,(several files open in Pixelmator, Snapheal, etc) AutoCAD, etc open at once my 8GB rMBP and barely dent the RAM.(20-30% memory pressure) If you aren't doing anything like aperture or Photoshop as you say, then 16GB is going to be extreme overkill.
It just depends on what's more important to you. I think this forum places too much emphasis on RAM, considering my experiences with 8GB. The SSD is technically upgradeable but at a ridiculously high cost. If need lots of the storage, go with 8/512GB. If storage isn't important, get 16/256 if the peace of mind is important to you.