Both of your videos show uses of a few techniques. Animating shapes and particles to name the prominent ones. To get good at anything, one must practice, practice, practice, and then do some more work on the technique you would like to master. The answers lie on this road.
I would suggest making some shapes that emulate what you like in these videos and then try and animate them in a similar fashion. Once you get some skills down, you can research tutorials, there are hundreds of free ones, in these you may find techniques you can apply to what you are trying to accomplish. Then you may wish to add to it by adding particles, again, the only way to get a handle on particle playground, or whatever, is to become intimate with it, trial and error are the keys to success.
just saying’…
Jon Merrifield
VFX Artist / Supervisor
PELi Studios, Austin TX