There is only jhana in which you are completely absorbed.
The 5 senses are shut down. it's impossible to practice any insight technique while in jhana.
the so called "Soft Jhana" or "full body jhana" happen as a result of too much body awareness,
the energy leaks to the body instead of the mind where it's suppose to go to which in return will also stop the development of the nimitta.
To stop this from happening you need to stop making your attention bounce to body parts and have a tight focus on the breath. when blissful energies arise in the body you have to ignore them no matter how overwhelming they are and keep the attention on the breath. your body must not move, you need to stay completely still, this way your body will start to begin to disappear. very soon the breath will become very ecstatic, usually your face and other parts of the body will become very blissful as well, but you need to keep ignoring that and keep attention on the breath, if all of a sudden the nimitta takes your mind away from the breath towards the nimitta, I advice that you return to the breath again and again until it's impossible to ignore the nimitta, this is where jhana absorption happens. you don't need to do anything special, you do nothing and let the experience unfold itself. you just enjoy the ride.