I own a Panamera and my husband owns an M850i. The Panamera drives like a Porsche, while the M850i is comparatively a boat. I'm not a big fan of how much suspension travel the M850i has; the Panamera has exactly the right amount to feel sporty but still comfortable, just like our 718 has.
Yes they are very functional compared to a 911. No they don’t drive like a 911.
Do they drive better than an Audi A7, Mercedes GT, BMW 8 series? That is debatable.