Sorry man, can't help you. I am an iOS/macOS dev, don't use iOS device personally. lol
But I can provide a solution which might/might not be feasible. If you have a NAS, install syncthing server on it and install synching client on your phone. Every time you are on your home network, it would automatically sync photos quietly. I don't know if syncthing exists on iOS, do check it out.
Still, this doesn't solve your original question, your photos getting mixed with WhatsApp crap. You would need to do some googling to figure that out, unfortunately.
Resilio sync is on iOS which seems to be a syncthing alternative, but it has limited free features.