Most of my mini-PCs have been Intel NUCs (or more recently an ASUS NUC). I also had some Gigabyte and Zotac mini-PCs and a few others from less well-known vendors. IIRC almost all had one such 20 Gb/s USB Type C port, unless they had one or two faster Thunderbolt ports.

With mini-PCs, I frequently use external SSDs, so I certainly used those ports at their full speed.

The only mini-PCs that I had in recent years without such a fast USB port were Arm-CPU based, as those are typically starved in fast peripheral interfaces in comparison with the Intel/AMD CPUs.