First let me say, I have never used either a Konica TC or a TC-X. But I do have a Konica Autoreflex T4.
Have you seen this reference which discusses the TC <
https://www.buhla.de/Foto/Konica/eTCHaupt.html>? And from the same author, this page about the TC-X <
https://www.buhla.de/Foto/Konica/eTC-XHaupt.html>?
If I understand correctly, the two cameras are very different from each other. The TC is made by Konica and is very similar to the T4, but missing a few features. More importantly for me -- I believe the TC has the same viewfinder as the T4, which is pretty good, as far as Konica viewfinders go. The viewfinders on the TC and T4 are said to be noticeably brighter than previous Konica models, and after owning a T3n, I agree.
As for the TC-X, that one is made by Cosina. I like the fact that the TC-X takes a modern battery (unlike the TC and T4). The fact that the TC-X is mostly plastic doesn't really bother me; I like light cameras! But the deal killer for me is the dimmer viewfinder in the TC-X, compared to the TC/T4. According to this review <
https://davidde.com/2018/12/06/konica-tc-x-slr-review/> the TC-X has a "...has a rather dark viewfinder for this class of camera and is easily its worst attribute."
I know, the quality of the viewfinder does not affect the image, but... One of the reasons I shoot film is because I enjoy the experience of using the old analog cameras, and part of that experience is the big, bright view through the pentaprisms of my Pentax cameras. While the viewfinder of my Konica T4 is not as bright as my Pentax MX, the T4 is acceptable to me -- but the Konica T3n viewfinder was not. From what I've read, I am guessing the TC-X viewfinder will be more like the T3n than like the T4?
Greg Weber, who is something of a Konica expert, also says this about the TC-X, "...drawbacks include its meter, which has a tendency to go out of regulation.." <
http://www.konicafiles.com/slr-bodies/-konica-tc-x-1985/>