There's a difference between off-meta, and borderline trolling or even full on trolling. Whether you accept it or not, metagames exist for a reason. Top tiers within said metas exist for a reason. You may be asking yourself: Why do they exist? Well, my friend, just call me the bus driver cus I'm taking you on a ride straight to school.
Metagames and tiers are esablished over a long course of time through various people playing certain things moreso than others. Break it down and every lane/roll has its top and low tiers champs whether that is by usage, viability, or both. Most of the time the usage stat comes from viability. Sometimes FotM happens, but even then said FotM has viability to it in a way that fits the current meta or makes a change to said meta in a way that is positive for itself. You mentioned Jungle Quinn. That by itself is not even off meta, but more along the lines of trolling. Why? Because it brings no CC other than an extremely short knockback and then on top of that has no real kill potential against things like Leona. As for your "Garen of Righteous Fire", what do the Liandry's and Abyssal actually give him? Nothing. That is what we like to call a waste of time and gold build and is completely inefficient for what Garen does as a Champion. In some cases, why do you think some champions simply aren't used in the competitive scene? Because they are not as viable. While they may be fun, they may have their own places in the game, in the overall meta they aren't used as much because they aren't as viable. People need to keep in mind that off-meta typically has to be used with a decent amount of skill and not everyone can pull it off.
All in all, this is a game and it's ok to have fun. However, make sure your team is ok with it beforehand, otherwise don't do it. It's not fair to the team because more than likely you're going to bring them down, whether you think so or not.