A+ rank struggling with speed in TETR.IO: finesse, queue reading?

Well the thing is I have played for a while in TETR.IO, I'm now on A+ and my QP2 PB has reached 950 meters but my sprint is trailing at 75 seconds. (This is probably due to a period of abusing MechHeart.) And now I'm at a point that I feel speed starts to cap my performance: often less than 1PPS at the top half of the board, thinking a lot.

Recently I have just adjusted my ARR to 0 and decided to go for finesse. But in many cases I just fling pieces over the edge unexpectedly and misdrops increased a lot. And many previous habits are difficult to revert. For example, I tend to rotate before horizontal movement, so finesse for an I piece in columns 2/3/8/9 are quite counterintuitive: for column 9, I tend to tap clockwise spin and hold right DAS at the same time, then tap left.

Is there a place to specifically play with finesse? I saw TE:C's All clear mode but I don't want to buy it. I've also tried playing 40L with finesse fault alert, but this seems not quite pure.

Another problem is that I would (more often than not) mess up my stack in a bunch of S/Z dependencies before topping out prematurely early in F6. This problem is not so significant when I have a clean well to build around but when downstacking cheese it really hits. I think this might be due to my inablility to read several next pieces and this may improve my speed too. So should I try to read several pieces as a whole, or I just need to train cheese race without considering too much?