Overriding: all depends on how you do it.
If you force a speed/duplex on one end, leave the other end at autoneg, it typically gets the speed correct, but mucks up duplex.
If instead of forcing you leave autoneg but specifically advertise a speed and duplex, if the other side is autoneg it works correctly.
So a 1G NIC can do 10/100/1000 for speed, and full/half for duplex. If you force "1000/full" leaving other side autoneg, you'll wind up with 1000/half.
If you advertise "I only do 1000/full" the autoneg works.