Greetings guys.
Honestly I love Krita. I love it so much, well done with the hard work on the app and its quality.
But it still isn't enough. It's never enough, even when it looks perfect. There are always bugs here and there and
the cycle almost never ends. I want to report issues but is it really a bug ? Because to me it sounds more like the
consequence of a bad design choice. I'll explain :

First issue follows. You see, it doesn't matter whether or not you have a powerful laptop. Over time, the brush cursor in
Krita starts to stutter and the more you work, the more this stutter is obvious. The issue happens mostly between
the start of a new stroke and the end of the previous one with a small brush. The faster you paint individual strokes the better you would notice the issue.
This happens on Windows 10 and even in version 4.3.0 of Krita.
Not sure if it's the same on a linux OS. I have a core i7 3rd gen CPU and an Nvidia GT 640M GPU. And the stroke rendering performance
itself is very smooth and doesn't slow down despite the stuttering cursor. This the first out of the two issues I want to report.

The reason I think it's a bad design choice is because, when computing resources are insufficient, it seems the app's code forcefully freezes the cursor's current position everytimes it renders a tip to compose any individual brush stroke. And it's true and obvious when you paint with a freaking huge brush(about 1400 pixels brush size).
Don't do that ! It's bad ! Don't put everything in one single rendering task. Separate the rendering processes in your code in these kinds of situation.
The brush cursor should always be smooth and not dependant on a stroke's rendering process, but only on the processing of a user's input. Please
optimize and fix this issue. Here are images to help yourself.

Krita 4.3.0 - Current cursor behavior
https://i.ibb.co/DWtzhXr/Worse-design.gif

Medibang Paint - Better Cursor behavior
https://i.ibb.co/NFYYBMZ/Better-Cursor.gif

Second issue has something to do with color picker and color shifting.
Here again there's a delay in the operations and I don't know why things this simple are laggy.
Picking a color should be extremely fast as soon as the user makes an input but it's not.
For some reason, selecting colors too has a bad delay that happens each time the ui of the color
docker updates its colors. Aside from all other possible optimizations, I would suggest that colors in the color selector
docker update only after the user commits color selection(After releasing the CTRL + CLICK shortcut).
These need optimizations in design and performance. I end here for the second issue.
Behold the lag when using the color picker(as the color updates, there should be zero lag no matter what)
https://i.ibb.co/rMSxjPL/colorpick-Lag.gif

Now that I reported these issues, here's my verdict: Krita has everything I would need as an artist and game designer in term of fucntionality,
seriously, I could use it to replace Photoshop entirely, but its quality regarding performance still has some flaws.

Please fix them issues and thank you for taking the time to read this.