What makes TPPI so special anyway? I took a look and there isnt even any minetweaker scripts. I guess most tweaks are in the tppitweaks.jar...?
Once you start up the pack(at least TPPI1) you receive a book that lists some of the big changes(TPPI welcome packet). You can also NEI search "tweak" to see changes made. I am honestly not sure what method is involved in all of the tweaks. I believe the TPPItweaks mod is mainly there to facilitate things as well as add in items to add to the crafting complexity/expense of other mods(like SFM items requiring AE Processors, Ender Quarry requires Unstable ingot tools, etc.). But it might do the recipe changes as well, dunno.
But obviously there is a lot more to it than what shows ingame. What I love about it is that it is a large pack with lots of options, yet it puts a lot of effort into balancing the mods against each other. For example one mod might be set to Hard mode recipes while another is set to Normal and another Easy mode in order to bring them to the same level. Like GT is in the pack but is configured and tweaked to play in a way that it feels just as advantageous/rewarding as Mekanism or any other mod.
It also make sure that cross mod combos does not negatively impact the gameplay experience. For example this:
No longer can you within a few minutes teleport lava from the nether to power your base. Teleporting stuff now requires a sizeable infrastructure and encourages you to seek out other power sources in the early game.
It also just generally prolongs everything. Quarries are very expensive. A normal BC quarry is modified by GT to require Stainless steel and Titanium, and all other Quarry methods are rebalanced to match that(more or less). So the "early game" is not just 30 mins, it might be a week or more of setting up stuff to achieve the goal of getting a quarry.