Hello, i have never played airsoft but i am going to rent a gun and play a bit in the near future, i am however quite fascinated by the technical and mechanical side especially with the guns and i have a few questions

With guns like the m4 what do different manufacturers/models do? With common guns like the m4 are all magazines compatible with each one or do they use different mag systems Ive heard about versions of gearboxes, i think these are used in AEGs, whats the difference between versions and manufacturers And lastly how hard is it to tinker or experiment with modifying guns if i eventually get one, what parts can be swapped out, how to find compatible parts etc Thanks, an interested person