From personal experience, the radiator does fit in, but it is almost glued to the plastic. (Unfortunately, I can't say in advance whether you need such a good cooler. But it's better to have a little too much cooling capacity than too little. You can use such things for years. If you want to upgrade your rig later, it's worth getting a better cooler now). I can't recommend a Pure Rock Slim, because the cooling performance is not much different from a Ryzen 5 stock cooler Wraith Stealth. (On my Ryzen 5 3600, so it's in the same performance class as your i5-10400F) I recommend the Noctua NH-D15 (16.50cm) as the cooler, because the price difference between the two coolers is only 8 Fr. and Noctua NH-D15 cools 5 Dgree better on average. And it comes with a very good thermal paste, which you no longer have to buy yourself. The GPU is probably too fast for the CPU if you're gaming in 1080p. If you're gaming in 1440p, it's a balanced system. A few more tips from me about this case. It's made of very thin metal, I accidentally bent the GPU bezel with very little force. And since the side window is plastic, it's really hard to clean compared to a glass window. For this, my recommendation: -If you need a side window: Fractal Meshify C TG -If not: Fractal Meshify C If they are too big for you, you can also buy the mini version of this one. Then the Dimension ones here are somewhat the same size as these cases. And yes, a matx motherboard fits easily into an ATX case. (Mini ITX too) Finally, the last one: IMPORTANT: If you don't need the PC urgently, WAIT! The new GPU from AMD and Nvidia will be released soon. They offer much more performance for the same price. (maybe a bit higher price, but it's worth to wait and see) Also the new CPU from AMD is coming out, but an i5-10400F should be enough for the next 3-5 years, if you only want to gamble. If you have any further questions, please don't hesitate to contact me. Best regards

this one is a version for matx boards the other one for standard atx... (larger mainboard)

Yes, the enclosure supports power supplies with form factor ATX up to 24cm

Well, if it's not enough, you can always add more fans.