everything is derived from System.Object so there is no problem outthere. MonoBehaviours are derived from System.Object too.
yes a Behaviour is a script that can be attached to a gameObject and become enabled/disabled and receive events and ...
just declare your variables public and derive from MonoBehaviour then the variables will be exposed. some types of variables don't have default inspectors so without writing editor scripts you can not show them. ulong for example can not be exposed. also keep in mind that properties like public int something {get;set} can not be exposed (pure variables only).