That will depend upon the cheat and how it is done.
Many level cheats will simply bump experience up to whatever. Not all games will check experience at all points though -- sometimes it is after legit gain, sometimes it is end of battle, sometimes it is after level up has passed, sometimes something else entirely/multiple avenues with you seemingly having either legit gain or end of battle for this one.
Disabling the basic giz max exp will still leave you with the max experience even if the save is restored to a virgin cart and an unmodified setup.
That is also just one scenario -- max exp is one thing, it might be enemies changed (though this is more for savestate approaches), if there is a multiplier (welcome back/we want to stretch this game out over a few months so daily sign in bonus) then that could have been pumped and whatever else might be in the equation can be twiddled (up to and including the game's own code but again that is more a problem with savestates that might keep the code in memory -- 3ds games will copy code from the cart to memory and use that, hence the option to do quite radical things in memory codes that in GBA and older might have been reserved for game genie/ROM level approaches).
You will then need to figure out what the cheat did and thus how to either reverse it or tweak it to more of an acceptable level*. Depending upon the game you may have to do something additional -- level up may only be level up rather than calculated based upon whatever and scaling back and forth.
*if it is like earlier games I imagine each character is separate so you might have to expand the cheat out over the other characters in the party/reserves. However the slide code setup that is maybe a variation on the theme of "repeat this every 5 lines/50 bytes/whatever" should also spread out over the rest of the characters so you might get away with the initial setup and then leaving it to propogate. Hopefully there are no underlevelled or there to ensure you don't lose a battle mentor type characters for this one, though said slide code should allow you the option to figure out where such things are even if only by trial and error.