Basically, it was this very matchup that got me into investigating playing alternate characters in tournaments (surprisingly it wasn't Sheik). There is not much to say here except that you will lose unless you are clearly more skilled than your opponent. Reason? Falco can short-hop laser you. To make matters worse, Falco can jump so high that there isn't much hope in trying to travel over the top of it. Since Young Link cannot duck under this nightmare either, you are completely doomed on Final Destination. Platforms are your only hope in this fight. Now that I've eliminated all your optimism for this match, let's begin, shall we?
You have to be extremely clever to win this fight. You cannot keep your distance because Falco will send lasers over to ruin your day. You have to move toward him. Avoid lasers as best you can and pull out a bomb. Good Falco players know not to use their down + B move to actually reflect projectiles (despite that being its original intent). However, if you can frustrate Falco with enough projectiles, oftentimes they become too tempted. If Falco reflects a projectile, he is stunned for a moment. It is a small moment, so that is why I recommended getting in close whenever possible. You need to exploit that opportunity whether it be grabbing him or down-smashing him off the edge.
If Falco starts attempting pillars, shield and roll. Young Link's roll is pretty slow, but it's really the safest option in that you are invincible for part of it. Shield until the shine barrage ceases and then roll forward. Your best bet at this point is to shuffle Young Link's up-air; it cuts through Falco's down-air. However, if you are recovering, make sure that you don't move too close to the edge when using your up + B third jump. Falco's down-air will cut right through that. Hover back from the ledge a tad to where only Young Link's Kokiri sword hits the ledge. Just before beginning your descent, smash forward to DI over and grab the ledge.
Thank goodness Falco is incredibly easy to edge-guard. His fire bird recovery is very short, so he does not have many options as far as trajectory is concerned. Usually a good edge-hog will suffice. If not, use bombs to mess him up (the fire bird usually cuts through arrows or boomerangs).
I used to believe that Fox was just as hard as Falco, but suddenly it dawned on me: matches against Fox are much faster than against Falco but far easier. Fox's lasers have no stun factor. That in itself gives Young Link a fighting chance. In addition to that, Young Link falls over when shined by Fox, so he cannot be infinitely wave-shined (unlike his older counterpart).
Fox is going to be in your face pretty much the whole time. He can sit back and fire lasers, but Young Link can still advance; the only caution here is that bombs are influenced by Fox's lasers, so never throw a bomb while a stream of lasers are coming at you. Fox is very good at close combat. His shine will be your undoing in most cases. It is imperative that you litter the area with projectiles. Do not fall prey to Fox's mind games. Just send in a projectile or three to do the job. Shuffling Young Link's neutral-air will prove quite beneficial. If Fox likes to drill-shine (shuffle his down-air into his down + B), shield until the nightmare is over, then shuffle up-airs.
The one beauty of fighting Fox is that he is a fast-faller. This makes him easy to combo/juggle. If you can catch Fox in an up-smash, most of the time you can follow up with another up-smash (if he is at low damage). You can also semi-chain grab Fox. Young Link's up-throw can be connected to multiple up-throws since the natural reaction for Fox is to shield. Don't overdo it; finish the last up-throw with a down-smash or double forward-smash!
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