i think that actually getting to a strength of GM is harder, but of course at world youth you have to be pretty high rated for your age group requirements. Also i believe that there is a Puzzle creating competition by FIDE that gives out a FIDE Master title for creating the best puzzle.
Is the title of World Youth Champion (U20) stronger than GM in general?

Yes. I believe it's more significant & rarer obviously, to win the world junior championship.
Just go back & average the ratings of the winners of the WJC for maybe the last 10-20 years & compare with the rating requirements of being a grandmaster which is 2500. Plus 3 norms.

Also, look at how many GM's there are in the WJC anyway. Clearly the winner has to prove they're better than a whole crowd of strong GM's (already legitimate GM's) just to win the tournament. And it's not a short tournament, it's not like it's a 5 or 7 round event. It's 11 games right (13 maybe? I haven't looked in a while). That's demonstrating something clearly over a stretch of games vs strong GM's & IM's.
I know winning the world youth at the eldest section gives one the title of GM anyway but I'm just wondering if nowadays or from as early as year 2000 is it more difficult to get that title than it is to get the GM title in general ?