Ah, I think I have a better understanding of the PCIe hardware protocol now. Feel a bit more confident regard a 2 x8 setup. Thanks.
Just for the record: my understanding is that the HW protocol performs a handshake which settles the number of lanes that will be used when establishing a link. And the PCIe standard is always backwards compatible, so things should work just fine even if I buy something that says PCIe 6.0 later. Or at least the lower layers of the protocol should be compatible. And as long bandwidth isn't an issue.
Ditching the Linux kernel is probably a good idea. Or at least run your own fork. Which I expect that many state actors and large companies already do. Also, I suspect that we'll see more large public kernel forks sooner rather than later. Even sooner if Linus retires.
To be honest, I don't care that much for myself. Guess I wasn't completely honest in OP. I'm just a nobody who gladly exposes his soft parts in exchange for cheap and easy access cat videos and general dopamine. Rather I'm thinking about what strategies policy makers, companies, NGOs and the general public should consider, as we crash into even more exciting times.