in general, its not good to have fumes in the cabin of the car from say -exhaust - oils - anti-freeze's and the like. the dip stick getting pushed out means that you could have a positive pressure in the crank case and could leed to leaking of engine fuilds, in turn it gets on hot items say the exhaust then gets into the cabin, so idealy youd want that pressure to be around 0 or a negitive pressure
if you have say a black color smoke out the exhaust pipes to a degree then thats ok as long as it not super black,
if it has a blue color to it then that can be an oil smoke -rings or valve guides - white color after its warmed up on a normal temp day -water -maybe head gaskets