"what recorder should I buy/dowloand?" I recommend OBS. It's free and works very well. Definitely wouldn't recommend buying any software for capturing PC gameplay considering the amount of free options. https://obsproject.com/

"Also i noticed that there isn't any Crusader Kings 2 speedrun, so... I'm the first?" There are a few CK2 speedruns, not sure if there's anything like what you've described: https://www.speedrun.com/ck2

Welcome aboard, I've never heard of Crusader Kings, but good luck on your runs!

Wellcomme to speedrun.com

why the hell did you necro a 2 year old post

It's always nice to welcome someone to the site but this person has been here 2 full years already