This game runs fairly well in CEMU but it's not perfect. There are still some graphical issues such as the cloud shadows in levels like World 1-1 being broken. Certain levels like World 1-5 and it's remixed variant are particularly problematic as they use a lot of dynamic textures which seem to not always render well but these levels can cause spikes in GPU utilisation as well, often resulting in reduced performance or outright crashing. The severity of these problems will depend entirely on your specs. I have read that levels besides World 1-5 such as Fort Fire Bros. are susceptible to this but I was not able to notice any issues in those levels on my system, but you may have a different experience if your system is lower spec than mine.
I also noticed that the Plessie levels are still kind of broken right now. It's kinda random and doesn't always happen, but sometimes Plessie will get stuck in a falling animation while in the water which prevents you from jumping. You can still complete and even 100% these levels if you can bonk her on an enemy or something to get her out of the falling state, though first time players may have trouble with this.
In my opinion, I wouldn't recommend trying to play through this game in CEMU right now if it's your first time playing the game, since there are enough potential issues to put a damper on the experience, but it's entirely up to you. If you're like me and have thoroughly played through the game on Wii U and just like trying to casually speed run specific levels on the odd occasion or something, then the game is mostly fine for that.
Any performance drops you notice outside of World 1-5 in this video are shader stutter since my shader cache for the game isn't quite complete.
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GPU: ASUS ROG Strix NVIDIA 1080 Ti OC Edition
CPU: Intel i7-8700K
Power Supply: Corsair RMi 1000
Motherboard: ASUS TUF Z370-PLUS GAMING
RAM: HyperX Predator 16GB - PC4-24000 - DIMM (3000 MHz)
HDD: Western Digital Black - 2TB - Desktop
SSD: Samsung 860 Evo 500GB M.2 SSD
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