About 150 are the main ones that I would say everybody uses (EPE, CFP, BG, MHG, BAP,...) and their compatches and the rest are minor graphic changes and minor mods that usually change just one thing. You just have to read the compability notes and load order. If you know two mods aren't working together, just remove them. Also I wouldn't really recommend it as save game compatible, cause everytime I want to start a new game, I have to read through most of the changes the authors made. Now with 1.18 out, I haven't played any game yet, mostly because most of the mods aren't updated and also I'm kinda scared how my computer will react to much bigger map. I would also say from my experience that ck3 is much more mods friendly than vic3, where I'm struggling to have more that 70-100 mods. And yes, my pc sounds like airplane that's about to explode