In scope of Pi4, anything higher than 3.0 is pointless.
The Pi only supports usb 3.0 5gbps.
So, using a super fast drive, like a pcie nvme that and do 10gbps etc, and/or enclosure that can do those speeds, is pointless.
And i did test the drive and enclosure, and got the same 480mbps or whatever it was, that the usb 3.0 5gbps spec gives, and same speeds using my other just sata to usb cable adatpers....so for me, the enclosure is working fine and not slowing anything down. (i only used this and the 2.5in drive for my pi server, cause it is just what i had lying in a shelf not being used at the time, the pi itself was also left over from a previous project and not being used)
I do not know what spec usb port the Shield Pro has, but i suspect is is same 3.0 5gbps (all i can find is just "2x USB 3.0")
On a different question/thought, I wonder if there is any real advantage to running this dedicated Channels DVR image on the Pi4 as your main server, since the OS is made by Channels, and is optimized very well for the pi, over using a normal pc with whatever Linux distro one prefers, with far "better" hardware.
I only know of the downsides of the pi, only having enough power for 1 transcode stream and slower commercial detection. (which is not a big deal for only 1 singe user)
For the short time I have had setup a 2nd server, for my mother to solely use, the Pi4 has been doing just fine.
But to answer your question....for external ssds, my only recommendation is a Samsung T7 or of that series of portable drives. I have a T3 model that is years old, and has seen extreme use over the years and still performs as well as day one with minimal wear reported. Hard drive enclosures, i have found over the many years of using them, are far less reliable and well built and have shyed away from using them entirely for the most part. But overall, I trust Vantec brand enclosures the most, their mid range or high end models.