My characters who are not my main character often go to do things which I don't tell them to do automatically. For example, attacking a certain enemies or disarming traps on their own will. That's not what I want to see.

Although I can disable Party AI by clicking on a button at bottom left corner, the rest of characters then don't follow my main character anymore. But I want them to follow my main character.

Is there a way to configure Party AI?

Sometimes the AI should be called artificial stupidity in this game.

You can set them to puppet mode, but then they do nothing at all unless you order them to do something.

This is how I do it:
Use the commands! Hold down the right mouse button over your character and a menu will show up. One point of this menu is enter command (sorry, I forgot what is written there exactly).

When you enter an area where you expect combat or traps (dungeon), go to a point where you want to fight and order your party to "stand your guard". They will stay there and do nothing. Now you go forward alone and lure a group of enemies to your party. When the enemies reach your party oder them to "attac nearest".

You should also order your party to wait and look for traps alone with your rogue. Try to take the trap and not just disarm it so you can sell it. Hold the right mouse button down over a trap to select this.

Warning:
1.) Your party will not attac enemies when you say "stand your guard" or "follow me". You must say "attac nearest" if you want them to attac on their own.
2.) Your commands affect only your party members but not the char you control yourself. So if you order your party to stay where they are and then you change your char, the char you just had might run away. To prevent this I do the following: press pause, order your party to do something, then select another char and give the same order again.
3.) Sometimes the problems 1 and 2 happen when you change party members. To prevent this, do the procedure written in 2 every time after you change party members.

When I tried to play this game the first time it got harder and harder until I had to quit. Later I found the answer. At some point of the game I ordered my party to follow me and I did not realize that they did not attac enemies from that point on.

Disabling the AI puts your party into 'puppet' mode, and you have to manage everything they do. A better alternative, in your case, is to leave it on, but adjust each member's settings. By default, casting is set to 'overkill', and disabling traps 'on'. Go into the settings and adjust as necessary. Press 'c' to bring up the character sheet, and go to the 'Behaviour' tab.

Edit: note also that you can use 'voice' commands (press 'v') to issue commands like 'wait', 'attack' etc.

Follow him as is the "best" option. My big problem you need to do that with each single new NPC. I usually disable almost everything except the attack enemies, and then only when I need mark the spells

By the way, not sure what I did but suddenly the summoning do not attack at least the order is given but was not the original behavior.

Thanks all. I have tried setting them to Attack Nearest. But after that, they run to attack enemies who are very far away. And they tend to go to attack enemies first before enemies notice us. IIRC, that didn't happen in the past. I want to try setting it back. Which option in the Issue Command list is the default one?

Btw, that druid automatically casts Lesser Restoration on herself every time after resting. How to prevent that?