Best way to do some research (that I know of - simple for me) is to take the model of gun and YouTube it. Then you will find many videos of people explaining their experiences with it. Gives you a good idea and you don't have to read
I checked some videos of the WE M4. Looks pretty badass.
2. I realized that most of magazines are hold up to 30rd bb's, how do you reload? Do you guys just carry many mags? or do you reload the bb's with one mag in the field?
Dude.. I don't know how you play, but I like to play realistically as I did for my first game. Lots of fun. Yes of course you carry more than 1 mag. Honestly, this one mag hi-cap deal that people do just makes me view them as a 14 year old with no experience. No joke.
You reload by pressing the mag release, and insert a new magazine.