Is it possible to make "changes" to a Vanilla 1.12.1 project server?

Such as to edit spells, like mana cost / coefficients / range / cooldowns. etc?

I might start up a vanilla classic wow 1.12.1 project, but am NOT looking to make another basic blizzlike server. Theres already too many of those. Wondering if any veterans here known if you can actually edit vanilla make such as make it Classic Plus.