stuff to do on DLL_PROCESS_ATTACH

it is guaranteed you can call any Kernel32.dll function on the DLL_PROCESS_ATTACH.
Calling any other function from other library is not ok, as the DLLs may not be loaded at that time (although your code links with those libs).
more info can be found in the J. Richter book. and J.Robbins say some problem he had in the past with some thread work in DLL_PROCESS_ATTACH.

using std lib functions between dlls

it is OK to have functions with variables of class vector or other std lib class, and call these functions between different DLLs executable modules or between EXE and DLLs, as long as both of the modules are linked in the same way to the C run time library (hence memory is alocated by the same code) .
info i think can be found in "C/C++ Run-Time Library Considerations", Chapter 6 in "Programming Apps for Windows" by J. Richter.