As a fighting game fanboy, I feel the need to point something out and drop some terminology.
You typically don't have more than one main. You can have one main and several "subs," but never more than one main. Your main is the one you feel MOST comfortable playing. Your subs are the ones you also feel comfortable playing, but they don't feel as natural to play as your main, but are still something you feel confident enough to pick if your main gets a bad pick, gets banned, or you just kinda wanna play something else for a while.
For example, in Blazblue, I'm a Noel main and a Ragna sub. I'm the most comfortable playing Noel, but I can always pick Ragna whenever I feel like it. (In fighting games, its a lot of work to learn a character, unlike league where it takes maybe 30 minutes tops, so its not uncommon to not have many subs at all.)
In league, I'm a Riven main, and a Shen, Leona, Varus, Morgana (mid) and Shyvana sub. Most of those subs are my go to pick for any different role, since I couldn't viably pick Riven into ADC or Support, so I'd pick Varus or Leona for that. However, any chance I get, I'm playing Riven.
So yea, kinda useless knowledge, but it helps clear up the difference between a main and a OTP in a completely different way.