It all depends on how far you want to take it. You gain expenses and lose convenience the further you get to “true 100% privacy and security”. The stuff Qubes recommends is among the best you can get when it comes to x86, but it’s still x86, and unless you’re working with 10+ year old hardware, you’re going to have intentional backdoors.
I would recommend a Qubes certified system if you must have x86. In fact I’m in the market for one myself at the moment because I specifically need Qubes.
@OvalZero beat me to the Talos II but the Lichee Console 4A is a promising RISC-V laptop. They have other form factors too.
I’d still prefer a 4G router plugged into an old laptop. Graphene OS is nice but the hardware is still Google. You can’t de-google the hardware, only the software.