You can use the cost of mindreading as an indication of the probable value, and skip mind reading any NPCs with a low experience cost. There is still the possibility you could get a shortcut that you wouldn't want to use (ie if it skips over subquests or tasks that would have given experience or decent loot), but you could either trust that on average you should still come out ahead, or save before talking to new NPCs and reload if you a mindreading attempt gives poor results.
There are lots of branching sidequests, so if you make different choices in subsequent playthroughs, you will get different quests available. Some quests have up to 20 possible solutions, though as the game progress there are fewer branching quests, as it starts t focus more on the main plot.
