>>535223334
100% percent sure I never installed any other additional mods about XPs, but I did use the "x0.75 XP Patch" version of that mod.
I did use the 5eSpells, but that was one year ago, on a different patch, and I think Mystra's Spells is now the go-to magic mod.

The creator of the mod is saying that, in the vanilla base game, there's a surplus of Xp point you can get to make sure you can get to Lv.12 by the end of the game, as a "failsafe": with no level cap, you *could* reach Lvl 17, by their calculations, or at least that's how I read it.

That being said, after looking into it a little bit more I suggest you to use a different mod such as https://www.nexusmods.com/baldursgate3/mods/279 since that one has many, many reports of bugs and things not working in Patch 8 (Gods forbid a girl made a typo) including the new classes etc.
I wish I could be more helpful, I lost my old 12Lvl+ save.