Also, do keep in mind that there are alot more than simply 4 aspects to modding Final Fantasy 7.
And from what you described, the 3rd and 4th one is essentially the same.
For instance, off the top of my head, there's the Model side as a whole, which includes splicing, importing, scratch and the battle <-> field conersions, as well as general reshaping. (Slayernext's tifa ponytail is a great example of the last one.)
There's kernal side, which includes enemy stat, player stat, attack and anything like that recalibrating, which determines how hard or easy the game is, changing equipment names, stats, effects, materia slots, what equipment we can get as well as changing enemy AI or creating entirely new enemies that also enables brand new player spells or twisting already existing ones into new animations, effects and rebalancings as a whole, and from this, you can combine new spells/limit breaks with unique models to create entirely new effects, such as changing matra magic into projectile swords, or changing blade beam into a dragon.
There's the event side, which determines the actual events that happen in the game, you can add or remove characters, include new boss battles, add new shops or do immensely time consuming aspects and do things like a 100% proper character replacement mod, such as making Sephiroth appear instead of Cloud, by going into every level, changing his associated hrp and animations so the game doesn't crash for an authentic experience, instead of just seeing Sephiroth be in Cloud's shoes with the normal animations.
The text side is an extensive of the event side, but there is an overall character limit within the game, and for each level, and if you exceed it, then you can have so many issues, from the game crashing, to events not working correctly.
There's more, but I really need to dash right now, as well as certain effects that can only work with a hybrid and combination of the others, I'll describe what I mean later.