I play this matchup basically every tourney as Michigan is the national Falcon state, lol. We have one PR level Falcon, a few HM worthy ones, and tons of other misc Falcons and players holding him as secondaries.
At first it was a challenging matchup but I feel like it's very simple once you figure it out.
You have no reason to ever approach Falcon. In fact, he'll usually approach you regardless of what you do, but that's beside the point. What you need to do is pressure him with pikmin toss to chip in some damage and get him to approach you. Just make sure you manage what you throw so you don't find yourself lacking pikmin when he gets close. Falcon's approach options are limited, and we vastly outrange him. Some common approaches include: Dash attack, dash grab, bair, shield. Dash attack and bair can be shielded and then punished (jab/grab), dash grab loses to a simple attack (fsmash/jab), and shield loses to, well, grab. You can also pivot grab any of his running approaches. Obviously in a real match it's not as simple as that, but my point is that his approaches are limited in easy to beat out with our range.
If the falcon likes to side b, having a pikmin latched onto him will trigger the attack and give you a free window.
Once you get the falcon offstage, it gets even easier. If he's forced to up b to the ledge, his recovery is super easy to gimp while keeping stage control. Every character has a very small window (one frame or something) as they're grabbing ledge where they're vulnerable to attack. The two moves for hitting this window are dtilt and dsmash. Dtilt can lead into another attack (fair, though not always guaranteed) and hit him offstage once more, racking on bonus damage, while dsmash can kill at higher percents.
If he does manage to reach the ledge, if you space yourself far enough away but where your fsmash can still reach the ledge, there isn't much he can do. Fsmash is really good at punishing most getups, and at that distance, a roll-getup will net you a dsmash.
The hardest part of this matchup is when you're offstage or trying to get back from the ledge yourself (IMO olimar's weakest point right there). You just have to know how the Falcon likes to tackle his offstage gimping game and play around it by mixing up your recovery's direction, airdodging, or throwing out an attack yourself. Never be afraid to go underneath to the other side of the stage, either.
In summary: Space him out with smashes, grabs, and pikmin tosses. Practice gimping his recovery, and always look out for gimps of his own.