The Motherboard ist the heart from the computer. It should be choosen correctly because it is one of the most important parts.
Our recommendation is the Asus ROG Strix B450-F Gaming II Mainboard because it is cheaper than others but it still offers enough potential to keep it for the next 3 years. You can take everyone from the B450 series but this is in my opinion the best solution. (My recommentation: Asus ROG Strix B450-F Gaming II Mainboard)
In fact you can take every chase you want on the condition that it supports the respective form factor of the Mainboard. In the case of the Oversteel Iridium RGB the size ATX is needed.(My recommendation : Oversteel Iridium RGB)
The processor is also a very important part from your pc. My personal recommendation is the AMD Ryzen 5700x, but if you want you can take everyone from the ryzen 5 series.(My recommentation: AMD Ryzen 5 5700X)
You can have the best Processor, but with bad RAM it wont be quicker than a 200 $ Pc. In my oppinion, RAM should at last have 3000mhz and i reccoment you to have at least 8 gb.(My recommentation: Crucial Ballistix BL2K8G30C15U4B 3000 MHz, DDR4, DRAM, 16GB (8GB x2), CL15)