- General:

It is very easy to get it into Plasma, but Plasma insists to manage background
of the root window (pkill plasmashell), and it doesn't even have a capability
to set different backdrop or picture to different desks.
(Read, cry and think how happy you are with FVWM!
https://forum.kde.org/viewtopic.php?f=67&t=141878 )

You should probably move or remove redundant KDE dock which covers FvwmButtons
Front Panel.

- Notice about wallpapers unser KDE Plasma:

Different wallpaper per workspace: Currently this is not available by default in
KDE and it doesn't seem like it will come soon, people can watch this bug:
https://bugs.kde.org/show_bug.cgi?id=341143
However it's an easy fix: https://store.kde.org/p/1197828/
Vallpaper is a powerful desktop setting widget (support for borders,
colors, slideshows, etc). The user can simply "cd ~/NsCDE/backer/ &&
convert *.pm *.jpg" and then set Vallpaper to those (remembering to
change Vallpaper from fill to tile).

- Logging out of Plasma session:

Put this into your ~/.NsCDE/NsCDE.conf:

SetEnv QuitCmd "Exec exec qdbus org.kde.ksmserver /KSMServer logout 0 0 0"

