TRIM is part of the Mac OS since Lion 10.7. It works on the boot SSD and any SATA III or NVMe SSD connected PCIe, SATA/eSATA or Thunderbolt. TRIM is not supported in the firmware of older SSDs including SATA II.
Disk Sensei cannot change that. Like all such utilities, it's an API for Terminal in that regards. DS has a few other tools that many find useful—again, APIs for functionality in the Mac OS. I have it. Before Yosemite 10.4.4, the correct Terminal sequence was complex and what worked on one version of the OS wouldn't on another—Cindori made that issue go away for free and if you wanted the other utilities, it cost you $10–$40.
Why doesn't it work on your RAID 0 array? I don't know—perhaps the firmware of your external bay.
Yea, there are two such units on the market. Apparently they work with the Apple TB2 to TB3 adapter. I'll probably go with the OWC since it has a pair of TB ports for daisy-chain. This will let me connect an old FireWire interface without hogging another of my TB3 ports. Two of those parts are being used by monitors.
Speed is not the issue. SATA III SSDs are slower than USB 3—I've tested this—so I gain nothing in that regard. I need to be able to run SMART tests on client drives. Like TRIM, this cannot be done over USB-anything. A dock takes a lot less room on my desk than my 2010 iMac with its eSATA port..
It's time for me to stick a fork in this topic. I'm done with it.