Hello Sriharsha,

If you are talking about the standards for PCB terminations then all that mentioned by you are standards based on the connectors as well as the PCB height. The Euro is one such and comes in standard sizes of 3U ( 100x160) and 6U ( 233.4x160). Once you have selcetd this size, then you need to select the connectors - these are also called EuroCard connectors and are available from 32pin to 96pin and pins arranged in three rows of a,b,c.

And if your current is more than 1Amp then you may have to use more pairs of pins or select the power Euro connectors that can handle 5Amps.

A visit to sites of Phoenix or Amphenol can answer lot of your queries.

Raghu