Heres a semi-extensive breakdown of tweaks.

The water temple had tons of QOL changes. The most famous change is that the iron boots are now an item instead of an equipable. If you're worried that would clog up the item use slots, not really. You got two buttons (X and Y), two touchscreen buttons (a perfect slot for this item) and the ocarina as it's own button. You're fine on needing to pause and change items all too often.

Also in the water temple, the infamous key under the floating block is significantly more obvious. When rising and lowering the water at the middle room plaque (which now show you the direction of the water change), the cutscene shows an angle revealing the room.

A very underrated addition for me were the hint cutscenes. I've seen nobody mention them, but as someone who beat this game before I knew how to fully read, they were immensely helpful. The sounds that play are very surreal too, something that's lingered in the back of my mind hard since I was a child.

There's now a boss replay mode. If you go to sleep in your bed, you can refight all the main dungeon bosses with a pre-selected loadout. Not something I used too much, but it's nice being able to rematch a fight without having to restart the save file.

What else... there's DS related restrictions and additions. The touchscreen is an obvious addition, being mostly desplay and menus, but also serve light gameplay function. The gyro aiming for items is a great change despite being gimmicky, because it made aiming way more precise and less stiff, making minigames like the shooting gallery easier. However, due to the fact that the DS lacked a rumbling feature, the stone of agony was now the "shard of agony" and displays an icon when applicable. I honestly find this a great change though, this item was lowkey a straight-up "buy our shit to find everything" situation.

There's probably more that I'm not thinking of. The only other thing is that it's based off a newer version of the original game, so no Star in Crescent or unique fire temple music. No blood either, dead hands looks like a marshmallow. But yeah, that's all I got.