In the link
details about Lubuntu using more system resources.
I had installed Lubuntu 18.04.5 32 bits in a notebook cpu intel single core 2 GHZ.
Lubuntu run fast using more or less 170 MB RAM and even not using video driver had a good performance watching internet videos.
Lubuntu 20.04 had changed to LXQT and use 378 MB RAM. After installing video drivers and adding few widgets use 470 MB RAM even thus is fast and is possible install in a machine with only 1 GB RAM.
More free RAM is good.
if is possible in future versions any configuration to Lubuntu use less RAM is good, but also need changes in LXQT.
Have another Linux distro that I not understand if is or not Ubuntu based that the OS use less of 200 MB RAM and has 32 bits version available , but has another side. That OS add own web links about politics.
About Lubuntu I need say thanks Lubuntu team.