I don't know if your question was directed to me, but I'll give you my opinion. Cut quality is more related to blade design (number of teeth, style tooth, set) and feed rate than anything else. All higher tension does is allow you to run at higher feed rates. Higher tension might also keep the blade tracking straighter when it hits some new grain orientation in the board but that's more anecdotal info. on my part than factual evidence.
Straightness is related to many factors, some of them related again to the blade (equal set, equal sharpness), some to how the blade is set up on the saw, and also tension. But you can get the same straightness at many tension levels; the only difference is in how fast a given tension allows you to feed the stock into the blade. This is why you read some people report that they get good results at low blade tension. That's true as long as the feed rate does not cause blade deflection, just as it is at higher tension. For any tension there is a maximum allowable feed rate where the teeth can clear the swarf and the beam strength is not exceeded. If the blade can't clear the swarf it doesn't matter how much tension you put on it, it will load up and refuse to cut any faster. And even at maximum blade tension there is a maximum feed rate at which point the beam strength will be exceeded; going any faster will cause the blade to bend and make a scalloped cut.
John