1) Are you talking about dash or standing grabs? Because if you're dash grabbing at all, you're definitely going to get beat out by his ftilt. If you're standing grab (which you should be doing), while it's somewhat easy to space incorrectly, you should be pretty safe. Forward Smash should out range his ftilt. There's a chance of him hitting the hurtbox on the Pikmin and canceling the attack, but he shouldn't be able to hit you with the ftilt if you're spacing it well enough.
That said, you usually aren't going to want to just sit at mid range and try to outrange Snake. Keep a bit of a distance and make him approach. Defensive Pikmin Toss with grabs/fsmash to cover the moments that he might soon try to approach during. Make sure to have the hitbox/grab out before he tries to come in, otherwise it'll most likely be too late with his huge frame advantage over Olimar.
Fair is good but only if you see an opening that's pretty much a guaranteed punish. Don't be predictable with it or you could easily eat a fair or a leave yourself open for a myriad of punishes.
2) Now Falco on the other hand, you are going to want to sit at mid range against. As you said, he does a good job in a camp battle against us and his close range game is ridiculous. Especially compared to ours. But he doesn't have very many good options if you're just outside of his range, but not so far that he can safely laser. Fsmash is great if you think he'll do a quick phantasm, as well as keeping pressure on him as well. Nair does well against it too, and if you want to get really fancy, utilt clanks with it in a way that leaves him vulnerable and re-grounds you to the neutral state so that it combos into upsmash beautifully. Try it out sometime.
Stay at long range for a little while just to throw some Pikmin for him to have to deal with. You aren't going to want to stay too far for long, but you don't want to abandon it completely. It's pretty easy to transition from camping long range to keeping pressure mid range, and force Falco to shift gears.
Stay away from him at low percents. It seems obvious, but it's a big deal. Camp the platforms until you get some percents on you. 20-25% should be fine. Don't give him the percents, by any means, make him work for it. If you bounce from platform to platform he should have a lot of trouble getting lasers or aerials on you, and you can get some free pikmin on him and maybe even a nair/fair or two. If you get under him and he's still on the platform, or higher, you can attempt juggle with a uair or pivot grab his landing. The pivot grab is safe since it will put you far enough away from him so that if he does avoid the grab, he'll be too far to punish you. The uair is safe since you'll already be in the air to retreat to your platform camping.
That said, don't be afraid to retreat to the air in general. If he's pressuring your shield, get off the ground. Don't let him get a free punish on a roll or try to throw out a move that he'll easily cancel with a jab. Not saying to jump away from him every time, but his answers to it are less so than most characters. Falco is by no means one of the best character at punishing Olimar being in the air.