TechRadar outlines the differences between different motherboard sizes and their different features and functionality ...
If you do want to shop overseas on a global store such as Newegg for your PC parts, these days you absolutely can do so. However, you may want to do yourself a favour and make batch purchases.
It also tells what components you should buy since not all PC parts fit into all motherboards. A good motherboard should ideally provide you with worry-free gaming lasting multiple CPU and GPU ...