As a beginner, I am always looking at experienced pianist to see how they play (the quest for the perfect technique to imitate I guess) but it's not an easy thing to do because a lot of extraordinarily talented musician have a very "non-standard" way of playing (Glenn Gould comes to my mind, in a different style also Keith Jarrett).
Recently, I was watching a concert of Jacques Loussier on Youtube and I think he has a very clean way of playing, I really admired how his fingers seems to be almost always in contact with the keyboard and glide effortlessly over the surface.
Here is the video:

I would be interested by the opinion of a more advanced pianist to know if it is really what to strive for

Liszt practised slow scales with his fingers not leaving the keys. When I started doing this my teacher noticed a fairly rapid transformation of my playing (and it accidentally cured my flying pinky).

I don't think you'll develop a great technique by watching great pianists but by listening to them. And it's not their playing you should be interested in as much as their training.

You start with a unique physiological hand structure and you need to develop different touches and different sounds. Your ear will tell you when you have the touch right for the piece you're working on and you need to practise the touch at varying speeds. This is where scales and arpeggios come into their own.

Check out these two videos of techniques I'm currently working on.

I really think it's best to work with an observant teacher, or at least observe what feels comfortable and not comfortable as you play. One person's cure is the other person's ailment because of the parts we don't see when writing over the Internet. I am learning to *not* have my fingers touching the keys all the time, and to have *more* movement overall in my playing. Someone else following what is helping me would end up getting worse, because of where they are at.

The other thing is that when I watch a video and try to copy what is being done, I may catch one thing and miss another. Josh Wright's first video, for example, is about creating an even legato sound in fast scales. He presents "down off down off" meaning when each note is released vis-a-vis other notes. What I'm noticing, which he doesn't mention, is the rotation in his hand and forearm as he moves from note to note. This may important in its own right. What is it that a person is demonstrating is doing, which he is not deliberately demonstrating? What is it that I will do as I think I am imitating that person's playing, in this respect? The only safe thing in my mind is to listen to your body and sound -- does it feel good and does it sound right? Even better is for someone to observe you. Very often what I thought I was doing as a student was actually on the money, but not always.

A great answer

I think I didn't express myself correctly, I do not try to copy, I was just amazed to see such a "clean playing" used in real life. Most of the time, the musicians I see get carried away by their emotion but here, all remains so "clean" (without scarifying the musicality), and that's what impressed me

I agree with you that Jacques Loussier seems to have the "perfect touch." Wonder if he's been playing since age 4. I enjoyed the video very much but would have liked it better without the background music...the piano by itself is far more beautiful than any other instrument of music to my taste. I enjoyed watching his hands move on the keyboard. To play with feeling without exaggerated movement is real talent and skill that I envy.