You guys must be virtuosos, I've taken it up again during this epoch but am nowhere near your level! I got to grade 5 when I was a kid.
I find a lot of it is being able to read the music (recognise the notes) fast enough. My sister's husband is reasonable at it but can't read music at all, just learnt some pieces from watching YouTube apparently...he does also tend to have a habit of playing with the pedal down all the time which makes everything around very ... legato
I quite like blues as well as classical.
I'm way, way off being a virtuoso. My sight reading is far too weak. This was brought home to me with a vengeance when our choir's Mus. Dir. came round a year or so ago to play some Mozart duets. Some of the easier ones I could do up to a pedestrian standard, but there were long periods in which I simply couldn't follow at all in the harder sections and he was playing on his own whilst I tried to be ready for the next easier bit! He told me afterwards that when he was at University, he used to sight-read duets with another student (it's possible he wasn't sight-reading I suppose) and then, when they had finished, they would play it again but transpose it up or down a semitone. That's a mind-bending skill. His duetting partner then got a job as an accompanist at the Royal Opera House.
With enough effort I can learn a piece which is perhaps not out of place in a concert hall (various Bach pieces, some Mozart sonatas, some Beethoven sonatas) and then, after enough effort, play them from memory. One of the biggest problems I am aware of is that my concentration goes and I make mistakes. I really don't like playing in front of other people, or recording myself, for this reason, and I tend to make more mistakes when I've got a microphone switched on. Mostly, my youtube recordings of me playing are a testament to Dez's editing skills as much as my proficiency. I recall the first time he made a video of me, it took about 2 hours of me playing so that he could condense it into 8 minutes or so for a Schumann impromptu. We had forgotten to move the clock on the mantelpiece and as I progress through the piece you can see the hands darting this way and that as he edited out my mistakes!
I am in awe of true virtuosos. I look at people like Andras Schiff or John Lill and their mastery shines through. When Schiff played the whole of Bach's preludes and fugues at the Proms, book 1 in 2017, book 2 in 2018, I marvelled that, firstly he was capable of memorising 2 hours' music without having to look at the score, but also that he had that many pieces "concert-ready" in one sitting. I wonder how many hours a day he has to practise in order to achieve that? I'd guess probably far fewer than one might expect. Something like the Goldberg variations is even harder in my view: it's technically more difficult than the preludes and fugues, and there's still an awful lot to play.
I was at a John Lill concert a couple of years ago and in the programme it stated that he was going to play a certain selection of pieces, but when he got to the platform he told us that he was expecting to play something else. He actually asked the audience which they would prefer to hear! I've forgotten now whether he stuck to the published programme or the one he was expecting, but it just goes to show exactly how good these people's memories must be that they have such a massive mental library of pieces that the can reel off without apparently batting an eyelid. If I remember correctly, he played a Haydn sonata, Beethoven's Appassionata, Brahms variations & fugue on a theme by Handel, and all 15 pieces from Schumann's "Kinderszenen".