Most desktops and mini-PCs can read simultaneously from only 2 internal M.2 SSDs, 1 of which is PCIe 5.0 and the other is PCIe 4.0.

They may have more M.2 sockets but usually except for the first all the others share the same PCIe 4.0 path.

Those 2 M.2 SSDs have a theoretical maximum aggregated throughput of 24 GByte/s, but what is achievable in practice is typically only slightly above 20 GB/s.

If you have 1 or 2 USB 4 / Thunderbolt 4 ports, the aggregated throughput can be increased with external SSDs, like in TFA.

With 2 internal SSDs and 2 fast external SSDs, a higher throughput than in TFA is possible.