Other components:
Kpple Menu = (custom Barbie head icon)
KDE's floating panels for taskbar and dock
Application Dashboard widget for dock (custom Barbie purse icon)
Virtual Desktop Bar widget used in dock (not recommended for Wayland)
Modern Clock widget used on desktop for date/time
Wunnderground Extended widget for weather in taskbar
gtk3-classic - found in Chaotic-AUR or AUR repos (makes both QT and GTK follow windows decorations)
I don't have a tutorial, but just learn KDE theming via youtube videos, etc., and you should not have an issue. The dock is KDE's floating panel. All the pieces are under the post that you need, theming elements, widgets, colors, etc. to turn it...Barbie. Have fun.
I am kind of new to lemmy myself, but from what I can find, I don't think it is implemented. There is a long Issue #317 open on the topic located on their github page. Might want to check that out.