Timeshift is great for getting your system back after a major fuckup. But i dont think it works as a backup solution that can be transplanted to other systems, but i never tried.
I use Kup to backup my important stuff. It comes with a kcm that integrates into KDEs settings menu and can do automated timed backups. Its a wrapper for bup. It also does Incremental backups.
Since you want an arch based dostro, i can highly recommend EndevourOS. Its comes with an easy to use installer, many desktop env options and a few quality of life tools like a comandline tool (nvidia-inst) to install nvidia drivers. And if you choose KDE Plasma in the installer, it will default to wayland.
AMD is still by far the better gpu choice for linux, but since explicit sync support is now in the 555 nvidia driver and kde plasma 6.1, most problems that nvidia had (i had) with wayland have seemingly just vanished. So no need to imeadiatly buy a new gpu.
I dont know about Gnome, but kde plasma “should” run and be usable with 1GB ram. At least ive seen some posts about people doing it. I think at minimum you would need to customize your ram related kernel parameters like swappiness, the watermark scale factor (kernel memory threshold for caching) and stuff like that. But i cant say ive ever run such a small system with a DE.