I have done pretty much everything I can to get smoother footage witbout a gimbal. Balanced props with the Dubro balancer, using some better quality 8045 carbon props but also the stock dji props do pretty well just not as good at higher speeds. I tried some other 8x5 carbon graupner clone props but these were a big fail, very well built and strong but had lots less lift and the quad also very unstable with them at low rpm no matter what I tried with gains.
Anti jello mount with a basic rubber band arou d it to stiffen it up a little and nd filters for nearly all daylight flights. did change motors to tiger motors mt-2216 after one of my stock ines got a little damaged in a crash, the motors I didnt do any balancing but they are smoother then the stock ones I think and a little more efficient. These 2 flights were also in pretty much dead calm conditions flown in atti mode. I dont think any one thing is the key just getting each part as smooth as possible but balancing props properly is the first step you need to take as most vibrations are from this and even when using a nearly full stock phantom it made a huge difference.