I think you can disable most of the toolbars in the main screen if it helps.
You can do that in the “Docks” menu in the topmost bar, unticking any you don’t need.
I think you can freely hide these, maybe more: stats, audio mixer, scene transitions, sources (after you have set up your capture source), scenes.
Then if it’s still a lot, you can untick these in the View menu besides Docks: scene/source list buttons, source toolbar, status bar.
At that point you only have the controls dock, the preview, and the thin top bar.
Don’t forget to reenable the sources dock and the audio mixer if you want to change those settings, though.
RAM usages on a 8GB system, 4 hours after boot.
There’s also various other things too. Now obviously, looking at the total used counter, these cannot be just summed up, there must be some overlap through shared libraries and such, because if I close my web browser and all I have open is Konsole, total memory usage drops to 2,35GB. 3rd party programs, like opensnitch and syncthing, only contribute 400 MB (opensnitch is surprisingly fat, but it’s UI is not efficient with the CPU either), so the system itself needs around 1,9 GB, but that’s a lot when all you have is 2 GB RAM.
Then, my system uses an additional 2 GB for cache purposes. Such an old system will probably have an older, much slower storage (unless upgraded, fortunately that’s often easy), and won’t have nearly any capacity to keep a filesystem cache.
I’m only using a single widget on the desktop to periodically run a command and display it’s results. Other than that, the taskbar panel has the default widgets.