I've been wanting something like this recently.

I want to occasionally have my "virtual computer" with me to use on other hardware. (ie my SO's laptop, my Steam Deck; hardware I mostly trust). I find myself bringing my laptop many places where I don't actually plan to use it, just in case some server goes down or the like.

Why Qemu though? Why not a Live USB? Is it just for the ease of treating the VM as a regular file for backup and transfers? I have little experience with Qemu.