[pso33]

I've updated to v2020.11 (from snapshot 2020-09-05 [ezdiy] after falling back from v2020.09 with met hangs and yet other slownesses). Also removed the whole applications/koreaders folder to get rid of any old file or config.

I have got rid of UI-slowness by now (browsing the menu) by 'Developer Options' -> 'Disable enhanced UI text shaping(text)'. For some reason, this device looks sensitive to it.

This is an additional finding besides decreasing DPI as much you can.
(And naturally, anyone who owns InkPad X have already disabled UI flashes in the normal 'E-ink settings' menu...)
Now the UI speed is acceptable in overall.

Some quirks I've spotted with v2020.11:
- background is white upon restart despite I've enabled 'Night mode' by menu; though I'm starting it as separate app, not as an file.
- couldn't download any dict via wifi, workaround was to transfer them from my kobo (where I also reinstalling from scratch, simultaneously). Only message appears to turn on wifi but nothing afterwards.

Tweaking "E-Ink settings\Refresh speed/fidelity" to "Level 3: low quality, fastest" on this device doesn't speedup anything. Instead, the page turn transitions get visible (trash pixels temporarily visible) but in overall same speed and quality with this extra visible flicker (some may find aesthetic).
The only benefit it has, it is visible what the device is working on.
Same true for Level 1 and 2 but not seeing any trash.

Summary: I recommend upgrading to v2020.11 for anyone having InkPad X now, as in general it looks stable (no hang) and speed is acceptable with proper tweaks.

Thanks for the developers reaching this milestone!