You just need to do a lot of different experiments trying different styles until you start to find what fits you the best. Though I believe I have found the style that works best for me, I still do some experiments trying new things. It takes time, but that is the only way to really find your style.
Nice work @Marcin! I think the first 2 have good form and look pretty good. I think you lost focus on form on the 3rd one and maybe started drawing more by contour. Overall, I think you are doing fine. You can do 'layers' to build up a finished drawing if you do your gestural work very light. I think a lot of people work that way. You can often see some of the underlying gesture below the finished work. It really depends on what style you are going for. I actually like the style of having a partially finished drawing that is mainly gestural. Keep it up!
It kind of depends on what you want to do with digital. I have focused a lot on digital portraits and figure paintings. I come from over 40 years of traditional art background. If you are interested in seeing some of my time lapse videos you can check them out here https://www.youtube.com/channel/UCxLr4Juph5m4vjU-ThkLoLA Marco Bucci has some great videos about digital painting in general. You also can't go wrong watching a ton of Sinix Design videos on digital painting. BoroCG has some great videos on YouTube as well.