Tubekites get their shape stability by inflating a Front Tube (Leading Edge) and one or several struts. The optimum pressure is around 6-8 psi (about 0.4-0.6 bar).
Softkites consist of two layers of flying cloth, which fill up with the wind in the cell chambers. Circulating trapped air supports the profile of the kite which makes it resemble a paraglider. You can find a comparison and detailed information on this topic in the following blog post by Kitedesigner Ralf Grösel under the following link: https://www.ralfgroeseldesign.com/blog/tube-vs-softkite-an-epic-battle