Just boot it up and play Critical mode as is. I really don't agree that EZ Codes make it more balanced, I'm a little thrown off to see that as such a common sentiment. The only thing I might agree with is POTENTIALLY using MP Recharge to workaround Critical Mode's pitiful MP bar, but even that seems more like cheating than balancing.
There are enough defensive options in KH3. HP Regen is not necessary. You can stack armor, air slide and guard are free and can cancel any of your moves, making everything a thousand times more reactable, and if you need it, Link spam makes you invulnerable. I can't speak for you, but if I got to the end card knowing that I used codes to negate portions of the challenge, I'd feel cheated out of a learning experience and I definitely wouldn't feel like I beat Critical mode under any circumstance.
I say learn the strats and tricks and just play it as is.
Difficulty and frustration in a game is really subjective - I prefer games that don't kill me all the time but makes me get on the edge of my seat almost dying, and then I die if I screw up again - in the most well balanced kh games I think the enemies can be really punishing but they won't kill you with only 1 hit, you'd still retain at least a little HP to Cure yourself and manage to strategize some way.
That said, "Proud" was my favorite difficulty setting in the rest of the games, but in KH3 I think Proud is waaaay too easy... I remember dying like 4 times overall and beating the game easily.
But in KH3 Critical (no codes), I played and felt like the enemies were way too strong for me to have fun - it didn't help that the LOADING times are a pain when you are dying over and over again in a section - which honestly is fine, I like trying again - but the loading times really killed the pace of the game for me. All the energy I was using moments ago in a battle - and now I'm supposedto wait like almost 1 minute for the game to boot. I couldn't enjoy the difficulty like I could with HD ReMixes.
So that's why I think EZ Codes DO balance the game's difficulty settings. The enemies are really really strong, but you also are! It is
fair, in my eyes and in my experience.
Difficulty and frustration in a game is really subjective
So to answer your question properly, OP, it really depends on your answer about:
how good you are at the game,
how much patience do you have for loading screens (if you have a standart ps4),
how much do you want to be punished for screwing up sometimes (total loss or 90% loss?)