I think it depends on the board.
Some Longboards are designed for performance and have thin rails which you can use to carve (look at drop knee turns which are similar to kissing the knees), but if the rails are thicker or the board is longer, you'll need to bring your weight onto the back foot so you can lift and pivot the nose.
Commented on HI everyone, has been a while since I...
18 Aug 19:49
On the pop up, I'd suggest you need to bring your back knee forward and under your chest. At the moment it goes out by the right elbow.
This is probably what is also compromising your stance.
You need to be more like this...