what kind of adders and multipliers architectures are used in IEEE.numeric_std.all
What do you mean "what kind"? The numeric_std package defines the interface in terms of VHDL functions (or operators) for adding and multiplying, and it defines the behavior as simple 32-bit integer arithmetic. 

The actual implementation in terms of gates does not concern the numeric_std package. Your synthesis tool will choose an appropriate implementation for you, which will be OK most of the time. Or you can configure your tool to choose an implementation that you want. Refer to the documentation of your synthesis tool for more info on how to do that.