This is the modpack HolyKnight uses for his minigame videos.
This modpack will run well on 4GB of RAM. You may want to increase the RAM if you're using heavy shaders.
This modpack is not really meant for survival, so you won't be finding all too many structures. This modpack is built to have fun with your friends with random items and armor. You could do some kind of mini game for loot, an all-out war, and anything in-between. This modpack will have you covered for your random multiplayer needs.