Ammo conservation actually becomes a thing in my survival playthrough, and in terms of playstyle, I found hanging back, slowly going through areas, and backtracking if enemies came a lot more useful. It features extremely tough enemies, as every single enemy gets huge damage and HP buffs, turning them into deadly bullet sponges. The damage is heavily amped up and makes dispatching of tougher enemies like AI turrets and Super Mutants a little bit easier Explosives become a godsend in Survival mode.

Changing the difficulty did not change the EXP rewards from a quest, or from killing an enemy, or from passing a speech check.

On Hard, Legendary spawns just seem a bit more plentiful.

On Easy, Legendary spawns are very 'hard' (haha) to come by.

Spawn rate of Legendary enemies (and thusly 'drop' rates of Legendary gear) is affected as you progress from Easy -> Hard.

On Hard, Swans could insta-kill me at times, like the Giants in Skyrim.

On Easy, Swans could hit me for as low as 12% of my total HP.

Damage you take is affected as you progress.

On Hard, Swans for me were taking 20+ light hits to kill.

On Easy, Swans for me were taking 4 light hits to kill.

Damage you deal is affected as you progress (Damage dealt is lowered).

I've brought my melee character and have quicksaved before a scripted Swan fight. I have tested most of this in game in a simple way. Gameplay changes that affect you as you change difficulty from Easy -> Very Hard -> Survival.

Fallout 4 increased spawns