So I've seen a few posts in this thread about the level of preparation that goes into one's boss battles, and there's a few things I have to say on this topic.
First and foremost: If you're like me and replay Pokémon games a lot and even casually can never seem to consistently get a clean fight against a certain Trainer, then making a plan isn't a bad thing. You bet I drew on all of my experience with Kukui in my UCL, because that man's AI does not mess around and his team is built to punish you hard if you treat his fight as being as straightforward as most Pokémon boss fights-a lot of times, he'll switch rather than Full Restore in a pinch if he has an answer to whatever you have on the field, especially with his lead Lycanroc. And his team is put together well enough that if he gets you on the back foot, he can easily ruin you outright. Having a plan in place for that kind of scenario is normal and should be encouraged.
On the other hand, if your rule set is forcing you to have a plan for every major battle because the occurrence of any death is stressing you out about how you'll manage later, then there's a good chance that whatever ruleset you're running isn't good for you, and that's fine. I'm going to be honest, after this UCL, I'm not sure I ever want to touch the idea of doing a monotype run for a long time. I mostly did it because I saw most other UCL runs using that ruleset, but it's been really eye-opening as to how even the most common types, like Flying, only have so many options for secondary typings, which makes certain Pokémon valued a lot more highly than others. Losing Pidgey in Mono-Flying Kanto is not a big deal, because you have Fearow, Dodrio, and even Farfetch'd if you are down bad for another Normal/Flying. Losing Gyarados in the same scenario, on the other hand, is outright devastation, because you have NO other Water type after that point, no matter what Kanto game you're playing-other options just don't exist in RBY, FRLG prevents trading Pokémon outside of the OG 151 until you beat the game and then some, and then they're back to just not existing again in LGPE. Again, one of the principles of the Nuzlocke challenge was to make you attached to your Pokémon, but eight straight runs of the monotype ruleset have seen me not being attached to the Pokémon as characters and friends, but as assets that I need to finish the game so I don't have to start it over. This isn't an outright condemnation of the Monotype ruleset, to be clear-if you enjoy that type of challenge, then go for it. What I am saying is don't force yourself into rulesets you don't like just for the prestige of it.