I have 22 matches of Young Link vs Peach and 29 matches of Young Link vs Jigglypuff from the modern Young Link era (2011-present) in this thread:
http://smashboards.com/threads/upda...ng-link-player-finder-video-directory.378209/
You can easily watch these matches and get a gist of how to play them all, but as far as I know, no one has analyzed and materialized the Young Link vs Floaty meta in the last few years, so I can't give you any guides per say.
The best advice I could offer is:
1. Camp them with projectiles, kill them with hit confirms
2. Don't be afraid to get a few nairs in neutral, or nair->nair combos
3. Don't be afraid to push harder for follow-ups (less so against Jigglypuff) but do be cautious about it
4. Grabs are decent against Peach, but do not try to grab Jigglypuff unless you're beyond positive it will land. Up-tilt into up-air is a pretty solid combo after grabbing a low-mid percent Peach.
5. Punish Jigglypuff's rest by throwing a bomb on one side of her, short hopping to the other side of her, using strong tilted upwards boomerang to knock her into the bomb, then follow it up with an aerial. This is like 40% damage.