RE the testec probe, if you take off the black plastic sleeve (just pull firmly) then the red plastic clip guide thing, you can put the black plastic sleeve back on with enough clearance to fit the BNC adapter. Spring clip would need the sleeve to be left off entirely. If you're poking around with the spring then you're probably using it for the low capacitive loading rather than high voltage so having a metal bit exposed to touch is less of an issue.
As for performance, I've tested these with a very fast rise time source and they behave rather well. Couldn't get the compensation 100% perfect in my setup (dead flat top of the waveform was elusive) but it was still a pretty good performance, especially for the price. Biggest downside I see is the friction fit spring clip - is a bit of a "how ya doing" way to retain it and they can come off easier than they should, especially as they get used a bit.