What kinds of airsoft gun should I get?

All of your options listed are good, airsoft guns can get very heavy if you're sprinting across large areas and continually moving. The weight of the gun is important but you can always get the heavier longer range gun and change your tactics. Post-up as a sniper from a stationary secure location instead of continually moving. Good camoflauge and concealment can reduce the importance of the gun weight if you're not moving continually.