I have some 1994 big box quality French doors for my entry.  One has a cane lock that goes into the threshold and header jamb. The other door latches to the door with the cane locks.  If the cane locks aren't engaged you can push hard and the doors will spread open.  Seals are pretty crap but then again so are the door panels with some shaker style panels that are 1/4" thick.  A quick scan with a FLIR camera shows these as one would expect as high heat loss areas.  

You can get high quality European style doors with multi point locking systems engaged via the handle that automatically pull against the header and threshold pins.  The better the quality the higher the price though.  

Be interested to see what you select.