Never used systemd-homed, but i know an alternative to full disk encryption is having the root partition unencrypted, and the home partition unlocked at boot. For a single user machine at least, i don’t see any difference when using it than unlocking at login. But then having 2 partitions is mandatory, and that may be a problem when running out of space.

You might want to look into Firejail, kinda complicated to setup but it’s made for this.

I think chroot could achieve this too but I don’t know how secure it is

I recommend NOT using Manjaro, they have many issues, most described here: https://manjarno.snorlax.sh/

for someone who wants an arch-based distro without tinkering too much there are other alternatives like endeavourOs, and I think Garuda too.

For someone who wants something that looks like windows, no need for Manjaro, just something with a desktop environment that looks like windows. I’d recommend Linux Mint, very simple to use (and for low end computers there is the XFCE edition), or distributions with KDE (fedora KDE, Kubuntu…) or maybe ZorinOS.

edit: also nobara Linux (based on fedora)may be good for games, they have a version that kinda feels like windows