Trim effects work correctly in IL-2 and DCS, meaning it moves the stick on aircraft where it should move, and doesn't move on aircraft where it shouldn't. The exception are aircraft from Razbam, they messed it up.
Overall the aircraft in DCS developed by ED follow the approach that FFB only transmits the effects coming from the control system, and nothing else. So no cockpit shakes, rumble, buffeting, esp. not on aircraft with hydraulic boosters. There is some in WWII aircraft. 3rd parties are free to implement additional FFB effects and sometimes they do. Like Heatblur or Deka.
In IL-2 there are additional rumble and shake effects out of the box. Sometimes even extras like a bobweight in Spit MkV.
