RECOMMENDED SETTINGS:
SEUS PTGI (or PTGI HRR Test) recommended. OptiFine needed.
will work with Nostalgia shader (and look decent as well!), SEUS Renewed, Chocapic Shaders (without reflections), BSL and more.

Options > Video Settings > Detail settings > Alternate Blocks must be turned ON
Options > Video Settings > Detail settings > Trees: Fancy or Smart
SEUS PTGI Shader Options > Raytracing Options > Geometry Trace Quality: 0
SEUS PTGI Shader Options > Choose Texture Resolution to be the same as the resolution of the texturepack

If you are getting OpenGL errors go to:
Options > Video settings > Others and then click "Show OpenGL Errors" and turn it OFF