Yes, you are right, if you put the crock pot lid on, you must be very aware of condensation getting into your oils. So mostly it is best left off.
And yes, for dried plant material that is aromatic, it is recommended not to use the warm method as this will increase the evaporation of aromatic compounds leaving you with a less potent product. You can put a lid on the jar within the crock pot if you really wish to do a warm extraction method due to speed. Just keep an eye on the temperature inside the jar in this case.