I was thinking a lot, but in the end i deciced to pick "I take a long rest as soon as my resources are used up" ...
But it dont seem exactly acurate, just closer to reality than other options ...
I dont rest when *all and every* of my resources are used ... sometimes one of my chracters have burned all spellsots, and another still have half ... i dont push them to continue on adventuring, even tho they posibly could.
And also not exactly when i use my last spellslot either ... since i allready know EA areas better than my own house ... i know wich group i can attack using cantrips only, so sometimes i just metagame and keep adventuring even tho i dont have much to fight with.
I refuse to rest in order to trigger conversation lately, they are still the same so i kinda lost interest in them completely ...
When it gets to romance night, i find out that lately i enjoy to troll my companions ...persuate Astarion to beg and then rejects him, meet with shadowheart gulp her wine and leave ... its surprisingly fun.
In second question i believe i picked 6-12 ...
As i said, with metaknowledge i dont see much reason to use spellslots in many combat situation, and if i REALLY wish to use something stronger, i usualy pick Scrolls or Short-rest restored features ...
Also, quite honestly it bothers me to rest in this game, so i kinda naturaly try to rest as little as possible, without litteraly restricting it.
