What I meant is that once you've gotten past the basics, hitting the right key becomes kinda automatic. You're way beyond the point where things become automatic (you're higher rank than me by a fair bit), so at this point you don't need to consciously think about what fingers you need to use to hit a note or anything.
In my experience, I know that I concentrate more on the right side notes and less on the left because I'm right handed, and I think that this conscious attention to the notes on the right side is actually slightly slowing me down because I'm thinking more about what I'm doing with that hand, instead of letting the automatic action that my brain has learned do it's thing. When you concentrate too much on what your hand is doing I think it interferes with your ability to automatically react to the notes. This is personal experience, so it might be different for other people, but that's what it seems like is happening to me. It's something I only noticed after many years of playing rhythm games.
since I play both 4k and 7k, I've noticed that finger positions for 4k seem a lot more "vertical" than for 7k. In 4k, most people (including me) tend to keep their fingers in a more upright position over the keys. There's also the consideration of whether you play 'wrist up' or 'wrist down'.
Do you hover your wrists in the air when playing, or keep them resting on something? That changes various things when you're playing. I tend to play wrist down, keeping my wrists on the table, but for certain kinds of patterns, such as jacks and jumptrills, I will actually switch to wrist up in order to use my whole arm to help with the up and down motion a bit. I find wrist up to be too tiring and uncomfortable to play all the time, but I think it has more advantages, especially at the skill level you are at.
Keep in mind, this is mostly from personal experience, and paying attention to things really good players have talked about. In one of his videos on youtube Etienne (one of the best 4k players) talked about the advantages and disadvantages of wrist up vs wrist down, but I can't remember everything he said, or which video it was. The rest of this is personal experience from ~15 years of playing rhythm games. But you are already a lot better than I have ever been, so I can't say I'm exactly an expert on technique.
It might be worthwhile discussing these things with some top players and see what they have to say.