Is it real that Arch users are rich and have mid level PCs and is always up to date?
I do have a powerful desktop running Arch (or rather EndeavourOS with the EndeavourOS packages slowly removed over time), but also a 15 year old netbook. There's plenty of up-to-date lightweight software in Arch repos, you don't need to limit yourself to old software.
Also it's not like a new version of GIMP is suddenly going to use double the memory if you use the same tools in it.
The biggest issue for the netbook is web browsing, but that's just about web pages being resource hogs nowadays. uBlock Origin and NoScript help massively. Trying to use an old web browser is IMHO a terrible idea - you'll end up with broken pages and a massive pile of security vulnerabilities.