I played Laijin's young link in a single friendly at apex (someone kicked us off our tv for a money match right afterward) but it was a pretty interesting single friendly. He started off with a three stock lead because I kept trying to approach, and he would hit me with bombs and stuff and get some good combo that killed me or Nana. Somehow I ended up winning though.
It was on FD so I'm not sure if it counts, but all I can remember is that I started playing conservatively and focusing on not getting hit. Instead of trying to catch or shield bombs, I would throw blizzards in his face whenever he pulled them and it seemed to work pretty well. He basically had to take the blizzard, or throw the bomb and watch it explode in his face. I don't remember boomerangs as well, but I think I just shielded or ice blocked them. Then I just waited for the opportunity to land moves, especially grab/f-smash/b-air. Young Link dies pretty quickly and has a lot of trouble killing solo Popo if you don't get hit by any bombs. I don't know if this helps at all, but it's the only good young link experience I have.
On platform stages I'd image it would be even campier, but you would still want to focus on being patient and not being tricked into making yourself vulnerable.
