Azen. He's probably the most famous patient player, just look at that guy do 3 fsmashes in a row and hit with every single one.
My second paragraph was mostly about staying in a spot where you're unpunishable and trying to pressure them into getting themselves into a bad position. For example, if you're pressuring a Marth with standing boomerangs (you'd be surprised), they might be tempted to jump. If you got Marth to jump you put him into a position where he's open to bombs or getting CC dsmashed (if he jumped at you). That's playing patient.
Approaching is Marth is weird. You really don't want to, but sometimes you have to (if they're really good at positioning). If you're approaching Marth you aren't playing patient, since it's a pretty bad thing to have to do. You should only approach Marth if you were forced to or if you have a bomb in your hand already.
Anyways, you need to base your decisions off what they're likely to do (the best option varies, you need to know your opponent's style and guess at what they'll do). Following up projectiles works against Marth because he has to either swat, dodge or shield them and all of those options give him some lag. If he uses a low lag option you just back off and keep playing it safe. If you make contact with a projectile you follow up depending on his DI, sometimes you follow up by getting another projectile out and sometimes you follow up with some real attacks. As long as you don't put yourself in real danger you're playing patiently.
I think that answers your question.