this is only a suggestion (as a test,) to see what happens by lowering the display resolution to 1920x1080. i think it has been suggested before but it if you haven't yet.
do this:
1. Change resolution to 1920x1080 within your radeon driver settings.
1a. Also, make certain there is no active scaling being done within these settings.
2. In Windows Display settings, set the scaling to 100%
and...
2a. the "Make Text Larger" is set to 100%.
2b. check resolution is the same as driver's 1920x1080
3. In MC set view>size> to 100%
3a. set font size in options to default size (japanese size = ?)
restart PC.
-open MC and stretch window to preferred size.
-open couple of other application/explorer windows (anything)
-try cascading the windows from the taskbar (right click), also try tiling and 'side by side'
- close the windows and leave the MC window open.
- close MC
-start MC to see if it opens at the last position and size.
by lowering resolution it may verify there is something odd with the interaction of your 4K display, driver and Windows.
i suggested this, because the only way i can get the MC window as small as yours, and smaller, is by altering these settings. after making the window the smallest size possible by dragging the corner (it has a stop limit,) changing these settings, you can drag window even smaller, beyond the previous stop limit, by dragging the corner again. other odd phenomenon with MC window sizes and positions were present. text being too big... window positions being off screen...
(this is with a 4K tv used as a monitor at 1920x1080 and changing to 4k resolution)
note, however, i have not experience your continuing phenomenon A. i also do not think this is a MC issue.
if your window continues to open small in the upper left position, this is a guess but, maybe there is a value written within the registry to open MC at this size and position.
maybe the value got written by a desktop utility used in the past (or malware) that can open program windows in a selected size position? this might explain the phenomenon appearing on the laptop..?
perhaps the same or similar desktop utility with this feature can correct the size/position -but i can not recommend one. -i also can not help with the registry.
you mentioned you could not find the link to the older Radeon drivers on the AMD site. the link is there under small text "previous drivers"
https://www.amd.com/en/support/previous-drivers/graphics/radeon-500-series/radeon-rx-500-series/radeon-rx-580 Only a fyi:
-my windows version is 2004 build (19041.508) x64
-windows update KB4571756 caused random 'crash to desktop' of MC with access violation of avcodec-lav* dll. Uninstalling the update fixed it. after reinstalling update KB4571756 the violation has not occurred.
-i am using an old version of nvidia driver 446.14 with an older version of hdaudio driver from 442.74. i do this because this hdaudio driver is the only one i know of that allows my receiver to properly (auto) change between hdmi and analog inputs without manual intervention. this is the best/stable combination for my pc. (latest driver is 456.38). my point is the newest driver may not always be best -use what works.
i hope you find a fix. my suggestion is to stick with the help you are receiving from tij and JimH. i am not trying to provide a solution of any sort, but at best, maybe a spark to an idea that will help.
ganbare umeuguis