Which I think was the real issue - all the cheap sci-fi shows had phoney looking exaust trails/smoke set against a star background.
I think you may be implying a pattern from a singular example that sticks out in your mind. From my recollection, "trails/smoke" against a background was the exception, not the rule. The singular exception is Battlestar Galactica, in which the exhaust trails are limited ONLY to the afterburner effect of the vipers and never lingers for long.
Also, he wanted something that looked signifigantly more advanced than the rockets people would see on the news or the fictional ones in the serials.
That wouldn't have been hard to do in the 1960s, considering those serials didn't depict rockets--or engines of any kind--in any real detail. I suppose Trek looked pretty sharp compared to, say, old Flash Gordon reels but if that's what Roddenberry was up against I kind of doubt he had something as
complicated as a low-gear gravity drive in mind.