The T series isn't worth it IMO. Second-hand non-T CPUs and PCs are usually the same price as the T ones, and you can achieve the same effect of lower power consumption by limiting the max clock speed of the non-T CPUs.
The Lenovo tiny series is not a thin-client; it's a mini PC. I wouldn't get a thin client since they're not designed to run much on them - a thin client literally just connects to a server via remote desktop. Get a mini PC or SFF PC at least.