I pretty much only use DMs to aim train, but I try to practice movement and crosshair placement. It's actually helped me a lot, like my aim has improved significantly as a result. I do think my sens/dpi combo is a little too high, but I've been using it for so long that I don't want to change it.
I'm a low elo player (G3 peak), but I do think that just practicing on specific aspects of taking gunfights, not just straight-up aim, will help a lot. Just working on movement or where you're putting your crosshair when holding angles, will honestly help your aim more than flicking, or spray control.
If you're wondering about how to improve performance, I think just try to improve your mental. Tbh, you probably have better aim than you think, you just have to make sure you're not getting frustrated from slow starts. I have shit mental, and something that helped was putting on music at low volume. It helped take my mind off the game to the point where even after slow starts my aim would pick up eventually. Sometimes all you really need is just to hit that one shot, and your aim just comes alive.