Well, there's a controller inside the SS T7 and then there's the one inside the PC. The one inside the T7 though is what will get to 100C if it's not properly heatsinked inside the case. With an M2 enclosure you would normally pick one based on the controller and the case material.
Plugable makes a good 10gbps case out of aluminum with a RTL9210 controller / chipset that performed best based on the M2's I had on hand and I tested a handful of them in the process of finding the best match. There were some ASM and VL chipsets / reviews but, IRL they didn't perform all that well.
SS is probably using some in house controller though. It's hard to say for sure unless there's a chance to do a tear down on one of them and see what's in the case.
80% of rated speed though is pretty good. The only way around speed limits though is to make your own with a drive + enclosure.