Some questions around Bluetooth Server

During port of Bluetooth for ESP32 some questions came up. Hopefully there is not too much "it helps if you can read" ;-)

• why do we use writable instead of writeable ? It took three coffee during test to recognize the missing e.
  
• the only event for a service is onWrite. Is there a reason not to use onRead ? I've added this during test for ESP32
  
• is there an option to define type of value for "mySpecialService" ? This can be done with a descriptor, but how would I define in javascript ? NRF connect supports byte, uint, text and some others.
  
• how would I define writeable for value only, and not for description ?
  
• how would I read or write value of a characteristic?