The third modpack, this one doesn't have a central objective, but an interest in giving the user as many things to choose to do and enjoy.
At least 3-3.5GiB of RAM is required to play the modpack, ~4GiB is the minimum recomended and ~5GiB should be enough to never run out of RAM in regular scenarios. If it can be spared, it's better to use 6 - 8 GiB to account for some memory leaks for now.
OptiFine HD U G8 is recommended and supported, also the only compatible version.