its a very old thing but tldr guns have to be unloaded before they can be loaded, if you try to load guns with full cargo your guns will unstack and just the one stack will reload as you do not have the space in cargo to unload the entire stack
Microwarp drives reserve a portion of your capacitor to work. If you are under cap pressure (having to tank a lot or being neuted), and know you don't need it anymore, you can offline it to gain more capacitor.