A question on the meaning and model of microphone impedance
1: Zm is possibly better then Rm, but actually usually what we care about is something pretty close to |Zm| being as the reactance is generally small enough to not risk forming audio band resonances with Cc and the preamp input capacitance, and the Q is low. 
Note that is this is NOT the case in guitar pickups or phono cartridges where stray capacitance very much can form resonances in the audio band....   

2: Generally yes, but note that nearly no capacitor microphone connects the capsule directly to an external cable, they all have an impedance converter (generally a  source follower or cascode or something) right at the capsule to convert the few Gohms you need at that point to get reasonable bass into something in the few hundred ohms region that can drive a cable. Thus a capacitor microphone is usually a low impedance mic in spite of the fact that the capsule needs to see a few Giga ohms of load.  

About the only real high Z mics were the old crystal (piezo) microphones once popular with cheap tape recorders (no need for an input transformer when using a valve as the preamp), and some slightly later dynamic designs that generally has a transformer in the body to give a level usable with said tape recorders.

These days almost everything you find will be low Z because gain is cheap and low Z sources are better behaved over long cables (Especially if the cable is balanced).