I’ve come to a point where i have to choose between two weapons for my offhand, and I’ve seen people talking about simming their gear. How do I do that?
Raidbots! Hang on, I’ll grab a link.
https://www.raidbots.com/simbot/gear
I use simulationcraft just download it, then download addon pretty easy to use after that if you need help just go to the website.
Alt-F4 
Thanx a lot everyone :D. They were pretty close, but I got an answer. Thanx again.
There may be a better addon for this now, but I really like Pawn and have used it for a long while. 
Simulationcraft is what you want, and the addon for it makes importing your stuff easier.
It will peg your CPU(s), especially if you tell it to estimate stat weights, so play around with the number of threads if your fans sound like a jet engine at full blast like mine do.
You should still sim with pawn and import the strings specific to your characters stats. I would advise against relying on the default but it is of course your character to play 
Thanx, everyone