Car A/C questions

Hi guys,

Apologies if this is in the wrong section. I'm after a car A/C (I know people don't normally like this topic) expert who I can reel off a few questions at..

Firstly the pressure switch, where is it commonly located and is there a hp and lp switch or is it a duel purpose one?

Upon researching I understand there are capillary and expansion valve systems the latter with a receiver and the capillary with an accumulator instead, is that correct? What differentiates the purpose for use?

I'm aware they use clutchless compressors also, does that mean the compressor can never be turned off?

thanks