Ive also met all three sisters, but only met them, not sure if theres anything more to do
On the main game screen of the game there is a button to call up the list of quests. Usually it is located near the upper right corner of the screen. It indicates the percentage of completion of the plot and personal quests of the characters.
Also, if the plot quests have ended, then when trying to get a new rumor, a message appears stating that the plot quests have ended.
As for the worlds you indicated: the strange guy in the forest is useless for now, as are the three sisters (relevant for the current stable version 0.71 and 0.72 beta). Therefore, focus on the screen with information about the quests.