When I am using the Simple CT resource pack on the "Redstone Ready" superflat preset, I go from around 200 fps to 5 fps. This is obviously because of the huge amount of sandstone in the world, and is fixed if I remove sandstone from the resource pack. I don't know if there is a simple way to fix this, but I figured I would submit this issue anyway as I can't see anyone else mentioning this.

I get the same fps with and without the resource pack in the world.

Please check if this bug is still happening in the 0.5.0 update. Thank you.

It is much better now. There still is a noticable impact on my framerate (especially with Sodium), but it's definitely playable now.