I would argue that Clarence is not the same character as Qiang.
Basically the same -- a schlubby but sharp-witted, Columbo-esque detective who's the main viewpoint character investigating the murders and the mystery behind them, and with the same surname and nickname. The context and details are changed, yes, but you could say the same of Holmes and Watson in Sherlock or Elementary, or of Bill Bixby's David Banner vis-a-vis the comics' Bruce Banner. He's obviously, recognizably a variation on the same character. That's how adaptations work. It doesn't have to be letter-precise to count.
I mean, it's quite possible that Clarence Shi's Chinese name is Shi Qiang, like how Benedict Wong's Cantonese name is Wong Hon-ban. If Shi Qiang had grown up in England instead of China, he would surely have adopted a Western given name. Regardless, it's clear that they chose "Clarence" because it bears something of a resemblance to "Qiang."
However, the story itself is "almost" entirely different, but designed to hit the main plot points to move the story forward.
You keep using the word "entirely." I do not think it means what you think it means.
Do you think The Magnificent Seven is "entirely different" from Seven Samurai? Adapting a story means changing it. This is a more international telling of the story, but I find it very recognizable as the same story as the novel. Its core ideas and plot beats are all there, and many of its crucial character beats are there even if they're assigned to different characters. I daresay it's closer to the novel than, say, Blade Runner is to Do Androids Dream of Electric Sheep?, and certainly a great deal closer than, say, the TV series FlashForward was to the novel.
I may not be remembering this correctly, but the name Trisolarans is the name Earth people call them--it doesn't matter what language that is in.
Of course it matters to the ear of the listener. I find "Trisolaran" a corny and cumbersome translation of San Ti Ren. So my personal preference is that San-Ti sounds better. "Trisolaran" is also inaccurate; San Ti Ren literally means "Three Body People," not "Three Sun People." And it should really be "Trisolarian" instead.