the guys from the forums don't know those things from the forums themselves. those things have specs. most in numbers. you can read system requirements of games you like to get an idea and then look up PC parts or complete PCs that exceed them. there are standards that say what parts generally fit together. when you know one part you want, that narrows down what other parts can be connected to it. for example, if you think the GPU is most important, it will determine the mainboard must have a certain connector for the card and also the power supply needs to fit, as well as the case dimensions to fit it inside. this is how you build/upgrade a PC. Some stores let you select only components that fit together for a configuration, like this German store for example will only let you choose a mainboard with an AM5 socket, if you selected a CPU that requires one and so on: https://www.alternate.de/PC/PC-Konfigurator