Texture pack lag on minecraft?

So lately I've gotten into this thing called Technic Launcher, and it's been fun so far. My computer is pretty decent and can run every modpack and most games from 2015 and 2016. But the problem is that when there's a modpack with a texture pack it will run at less than 3 fps. I can't even make a world. And when I'm playing other modpacks like Tekkit or Hexxit, I get about 100-350 FPS.

Here are my specs for anybody that's wondering.

Processor: Interl i7-6700HQ 2.7 GHz
RAM: 8GB
Windows 10
64-Bit
GPU: GTX 950m 2gb

Beats me
.