ATX is a full-size motherboard form factor, while Micro-ATX is a smaller version of the ATX form factor.ATX motherboards have more expansion slots and ports compared to MATX motherboards which are great for expandability.For MATX - You will not be able to fit in the higher end graphics cards like the RTX 3080, RTX 3080 Ti & the latest 40 series due to the physical constraints. If you are not looking to upgrade to these high-end graphics card (costing $2,000+) in the future, the MATX configuration is good for you as it is the most value for money build.In any case, if you do plan to upgrade your graphics card in the future, all you would need is a case change.