Well, I solved pyra and skewb without a guide. That's about it, if you don't count big cubes. Like I never watched a tutorial on 7x7, I just kinda did it with skills from 5x5.
For me probably the 5x5 I solved with my 4x4 knowledge I could probably work out higher order nxn puzzles if I tried them (I don't even own a 5x5 my school has one for some reason).
I made it through the reduction/rebuild on the mf8 Big Dipper with just previous puzzle knowledge and techniques. Sadly, a pop brought that journey to a screeching halt. I should get a second chance at that puzzle some time next week, so hopefully I'll make it to the end.