1: Why is the debug tool changing the dynamic of the behaviour when it is used?It is because in order to visually follow the execution of the nodes, the execution has to be slowed down. If it was not slowed down, the nodes are executed so fast, you would not be able to follow the execution and it would not be useful.
It is very clear that when it was active, The NPC's wandering was erratic and weird, Yet when it was inactive, The wandering looked normal and more natural.
The wandering is affected because of this.
Could something like this be added for scripts? Sure, It's easy enough to add a notify to areas to make sure they are working, But you can do the same thing with NPCs. In addition, Having a visual indicator as to where a script is failing would be really useful.
Especially if the game told you what the script was trying to do.
I can't tell you how many times I've messed up on a script by accidentally using global history. Those kinds of problems aren't easily noticed, And some way to quickly spot them would be great.
It may be redundant at times, But I think it would be really useful.