This might be a question for r/hardware or another sub, but I think it's NVMe for the near future.

SATA3 has maximum 6Gbps which is not much by today's standards

You may be sleeping on SATA. In a race, yes, PCIe drives are much faster. But for many uses, PCIe and SATA SSDs feel about the same. I definitely couldn't tell the difference while just using an OS if I wasn't looking for it, and short of a file transfer I'm not convinced I could tell even if I was looking.

It depends on the application, of course, but for multi-booting I'd be fine with SATA drives. Windows feels fine on every SSD I've used, NVMe or SATA, and I use little SATA drives for my home server (Unraid) and living room PC (Pop!_OS, formerly Ubuntu) OS installations.