In general, creating clip overlaps by dragging clips in the
parent track should and will create new lanes to resolve the "collision", regardless of the status of NDME.
When overlaps are created by dragging in
lanes, the collisions will be resolved by cropping the clip in the 'landing" zone to make way for the moved clip. If NDME is enabled, the cropping is non-destructive (i.e. cropped out notes can be recovered by slip-editing the clip boundary back out). If NDME is disabled, the notes will be destructively removed from the clip (but as noted above, you may have to Apply Trimming manually).
AFAIK, this all pretty much works as designed. That said, I know of a several other things that work differently/unexpectedly/unintuitively/incorrectly, depending on the status of NDME. One was fixed fairly recently (terminal controller events not preserved when copying or bouncing clips with NDME
disabled). In general I find that MIDI editing is most intuitive and the results are most musically useful when NDME is disabled. But any time I encounter an unexpected result when moving/copying/pasting/groove-clipping MIDI, I retry with NDME in the opposite state, and usually get what I want.