Mech is really well optimized. For the hundreds of people that have played it I've only had 2-3 lag complaints (and they were fps complaints probably related to the resourcepack). I'm actually kind of surprised how well it runs based on it's size (over 15000 commands), but it works very well.
I would agree with Hashs that there should be a category to represent a lot of game changing content. Take my project Mechanization for example: it adds blocks, items, cosmetics, world gen, player mechanics, game mechanics, and QoL features. If it was a mod it would just get shoved in the Tech category, but there aren't enough 'tech' datapacks for that.
Few names I can recommend would be Overhaul, Game-Altering, or Expansive.