After writing this, I came to conclusion best description of what i need is "fullscreen file-manager"
I want to use my desktop (as in app, that shows my "~/Deksop" folder on top of custom wallpaper) for browsing files. I spend a lot of time browsing filesystem and I need nice background behind and no GUI-buttons taking space. I need to just click into folders backspace to go back, more options could come in only as I hover near to top.
Closest thing, I've seen to it, were topics about changing background of file manager, but that's not really what I want, I want whole file browsing experience to be based on desktop, something close to android devices.
Maybe you can straight-up install android desktop to use with Ubuntu? I don't want android system, just it's desktop setup.
My concrete need would be : file manager that can hide all it's gui and roll it down from top of screen (or even not have it), and can be configured to work as background (always below other apps).. Pretty sure second part is just what can be handled by window manager with any app..
I cannot do it with thunar, as I can't really make it fully full-screen, also it doesn't allow me to put icons whenever I want, they are top-left stacked. I will check out other file managers.