Maximum USB4 speed on Apple Mini 2018

On a 2018 Mini, you will not get anywhere close to USB4 speeds primarily since it does not support USB4. Don't waste your money on a USB4 drive as the max speed "theoretical" speeds supported are in the 10-20 Gb/s range and many have been disappointed that they don't get those speeds as you apparently need "just the right drive" to get close.

Thunderbolt4 "theoretical" speeds are not any higher than Thunderbolt3. Thunderbolt4 however adds a lot of refinements and requirements that Thunderbolt3 does not have.

Bottom line, real world Thunderbolt3/4 speeds are generally in the 2400 MB/sec range with some drives a little faster and others a little slower. Expect real world speeds in the 1800-2700 MB/s range with read speeds generally faster than write speeds. So, sticking a 5000 MB/s SSD it a Thunderbolt enclosure is a waste of money.

That 40Gbps is the theoretical electrical rating, but you will note that when they tested it on a MacBook Pro (unspecified) using a Samsung PCIe4 NVME 980Pro, they only realized read speeds up to 2505MB/s and write speeds up to 2,454MB/s. That Samsung card is rated at 7000MB/s read and 5000MB/s write, and they are no where close to achieving that 40Gbps bandwidth that they advertise.

Not only is the Ankmax throttling the 980Pro performance potential, it is actually slower than the internal SSD in my 2021 16-inch MacBook Pro M1 Pro. They want you to fixate on that 40Gbps number, not the realworld performance that they admit too.

I would not purchase this external enclosure.

The https://eshop.macsales.com/shop/owc-envoy-pro-sx at 2847MB/s is more realistic and probable all that you will get with that piece mill external SSD. Plus Envoy Pro SX has a slightly better price point, a 3yr warranty and an awesome support staff if you need help.