I don't own one but since it is not widespread in the English speaking world just my 2 cents.
If you want more infos, have a look at the German forum:
https://www.e-reader-forum.de/t/neues-inkpad-x.153713/
1) Only complains I read so far from people who owned them where some minor things regarding the firmware which pocketbook promised to solve soon.
2) Sleeve is not included, costs around 20€, but screen is sturdy since they have no glass parts in it. They don't advertise the almost unbreakable screen though.
3) All Pocketbooks provide a folder view, including subfolders etc.
4) Calibre export is depending on the export template which takes a while to adapt to new devices. Using other Pocketbook export templates should work.