Mid towers basically have exactly enough room to fit components in, while full towers are bigger but give you more room to work with
Fully modular power supplies allow you to remove all cables to store them, semi allows you to remove peripheral cables if you aren't using them but the motherboard and CPU power cables are permanently fixed (this is only a problem if you want custom length or sleeved cables), and non-modular has no removable cables, making it both awful to install and will make your cable management look like was if you can't find a good spot to tuck unused cabling