(MOST) Relevant Cookies ranked by difficulty of use (+ Explanations)
I've included MOST cookies that I've seen used sometimes. If a cookie you use isn't on here, ask me and i can give you some explanations on them
A+ Tier :
Peach Cookie : Hardest cookie to use by far, in my opinions. If you see her in a guide in breakout or honestly anywhere, there's always memorization you must do with her magic candy. Sometimes it's simple (Like collecting more jellies or breaking obstacles),
But sometimes you have to land a 60fps frame perfect, spam jump 5-6 times perfectly, do a single jump after perfect to avoid a bonus time letter and you just want to cry after 160 attempts and no successes. Oh yeah i should mention the RNG aspect of her, many times you'll have to hope the obstacles in your skill are JUST the right way and you can collect the rainbow bear jellies, paradise coins etc, AFTER you do that horrid frame perfect
Jumping over blast mode, delaying blast mode, getting blast mode early, and doing jumps at 0 energy for optimal revival (Like most revival cookies) is also more challenging things about using her
Nimbus Cake Cookie : Don't use him in trophy race, no matter how good the points look. You often have to memorize magic candy uses, it's often easy to miss rainbow bear jellies because his skill is clunky. When he is used with revival treasures, you can bet that you have to hit a very precise input to buy extra time to sneak in another skill, which if you can imagine is inconsistent and is not worth the risk 7th place in trophy race after you mess it up. Pick a different combi, I'm begging you.
Longjing Tea Cookie : Quite a few jellycon cookies here, but Longjing Tea is the most punishing of them, because unlike the rest his skill doesn't affect the whole screen, so you are sometimes forced to do really memory heavy and unconventional movements to maximize points, and it's all too easy to mess up. If he's used as a relay, the first runner often needs very specific distance control, which if you fail it's not worth using Longjing Tea anymore due to point loss
Choco Bark Cookie : The most memory intensive cookie here, because he is completely manual with 9 skill charges every cycle. + Distance control as well, you have to do really well in blast mode parts to break as many obstacles as you can, and if you press slightly too late without any powerups, you collide or fall because this is such a risky and inconsistent cookie to use
A Tier:
Fig Cookie : If you use Fig + Paradise Compass, drop them to B or B+. 90% of their difficulty is from collecting jellies while traveling extremely quick during their skill, and also controlling you distance while doing so. If you use Paradise Compass, they are much easier as rainbow bear jellies are attracted to you along with other things, but as an example in the Spider Mansion Breakout, fig requires specific movements to collect as many giant coins as they can.
Dreamjelly & Entremet Cookie : Less difficult jellycon cookies, unlike Longjing Tea the penalty for messing up isn't too big, and the abilities being more sparse and affecting everything makes them easier, although for a good score you have to pay attention to little movements to turn a couple more jellies to their skill
Knight & Lemon Cookie : Bonus time runners. Memorize distance control first of all, and then hope you do well on bonus time if you don't have the shield treasure, requires precise movements (HARD) in bonus time, nothing else special.
Cherry Cola & Bamboo Blade Cookie : Requires specific distance control to work, like delaying blast powerups. Also Bamboo Blade has a thing where you click right before the timer runs out so you use your slash but barely travel any distance from it. Cherry Cola's lack of super magnetism makes her annoying in collection and destruction.
B+ Tier:
With the exception of Candy Corn and Lollipop who require miserably difficult collection to maximize points (Arguably A tier), everyone else here is just some memory. Not that much but can mess you up, Melon Soda sometimes needs proper distance control for the first runner if used as a relay or else you will miss some jellies because of her magic candy.
B Tier :
Memory like B+ tier, but even less, because the memory sections are almost exclusively during their skill, which happens in strict intervals, so it's easier to keep track. I know Halite Gauntlet spamming is sometimes used for certain combis but it's not major enough 90% of the time to warrant a higher difficulty here, though she can become quite hard because of that. Dreamweaver + Epic pet can be tricky because of certain potion delay methods, Whipped Cream requires good jumps near the end (Before Revival), Cream Puff with her occasional blast mode during skill can mess up jelly collection specifically.
Not Hard : Almost always straightforward, some control is needed but no unique challenges, and certainly none that'll mess you up bad.
Anyways this is my opinion from my experience playing this game, thanks for reading