For the Ocarina of Time 3D remastering Nintendo worked with Grezzo a Japanese game developer founded by one of the original developers on Secret of Mana. Grezzo has had a hand in a ton of Zelda games such as Majoras Mask 3D, Four Swords Anniversary Edition and Legend of Zelda Triforce Heroes. All that said the partnership with Grezzo and Nintendo was well suited because the port is top notch and fixes every problem I mentioned above and even goes beyond that. I'm including a link to The Legend of Zelda Wiki that outlines all the differences below but a couple standouts are the enhanced graphics, revamped item system and inclusion of the Master Quest after you complete the base game.
Recently I just made it to the Temple of Time and got the Hookshot from the race with Dempe. Personally I think the first part of the game up to the Temple of Time is the best paced story, gameplay and dungeon parts but if you like more complicated dungeons everything after the Forest Temple is for you. There are a few times in the game where what the game wants you to go next isn't obvious and Google can help a suffering memory when you are absolutely lost on what to do.
One thing that's nice about these remakes is that Nintendo can keep porting them forward on newer systems so if you missed Ocarina originally you might have a chance to play it on the Switch. I hope Nintendo keeps these old games fresh on newer systems and these kinds of remasters make them even more relevant to modern audiences. That said, if you absolutely need to play Ocarina of time in it's original 20 FPS glory getting out your old Nintendo 64 will always be an option.
I've included a speedrun of Ocarina of Time 3D from a couple days ago run at the Awesome Games Done Quick game charity stream so if you are looking to understand more how the remake looks I recommend you press play as the speedrunner Benstephens56 doesn't disappoint!