Favorite Distros?

recommendation: something simple like fedora

favourite: either NixOS or gentoo

Is there actually a big difference in lightweightness between distros, that does not go back to the Desktop Environment and used Software?

Fedora Budgie spin. Budgie has been my fav on my old Lenovo T510 and my Acer Ryzen 3 laptop, to the point I'm thinking of converting all my stuff to it.

Clean and light bout 600 - 640 MB RAM at boot.

TL;DR: I'd say EndeavourOS.

Note that as a general rule, the more lightweight a distro is at "run-time", the heavier it is at "configure-time", because you'll have to make choices depending on your needs to get better performance. As an example, probably the lightest weight distro is Gentoo, thanks to compiler optimization and USE flags. But it's a distro with an incredibly steep learning curve. On the other side of the spectrum, there's Ubuntu, which is one of the distros that requires least user configuration, but is also a resource hog. In my opinion EndeavourOS strikes a good balance between the two factors (Disclaimer: I don't daily drive it. I've used it enough to know I can recommend it)

You can Try Fedora Workstation. its good for beginners and advanced users alike. It has brought hardware support and comes with flatpak - a large repository of software.