There have been some discussions about sound in [sci-fi] space, particularly about whether you could hear the sound of an explosion during a space battle. Somebody showed how it could be theoretically possible. The main point is that hearing explosions during space battles makes them more exciting. ST:TOS did this in "The Ultimate Computer" by showing the bridge of Bob Wesley's ship when it was it by a phaser blast. Inside the ship, no problem. So, a bit of poetic license and suspension of disbelief adds to the enjoyment.
The series was just getting started. "Balance of Terror" was a loose adaptation of the Robert Mitchum film "The Enemy Below", which was about a U.S. Navy destroyer and German U-Boat during WWII. The whole thing about the sound was taken from that. At the time, not many television writers had experience with sci-fi. ST:TOS needed plots. So, they borrowed heavily where they could.
ST:TOS had a number of inconsistencies that varied from episode to episode. They were still developing the canon. By Gene Roddenberry's own admission, the reason for the "transporter" was that "he couldn't figure out how to land this thing" where "thing" meant the starship. Plus, the special effects for the transporter were far less costly than showing the ship land/takeoff, etc.
In most ST episodes, put antimatter in contact with matter and it explodes [except under controlled warp engine conditions]. This means any matter and any antimatter. In one episode, somebody said "There's less than one ounce of antimatter here, but it's more powerful than 10,000 cobalt bombs".
However, in "The Alternative Factor", there were two universes, one of matter, one of antimatter. Each universe had a copy of a given person. In this case, Lazarus. Matter Lazarus [who went insane] wanted to meet his antimatter counterpart and destroy both universes. Matter Kirk got sent to the antimatter universe. Met with antimatter Lazarus [the sane one]. No explosion because they needed to be the alternate version of the same person. Made for a great story, but violated canon from all other episodes.
By the time ST:TNG rolled around, the canon was well established enough that you had "continuity" editors that would spot the canon violations. Hence, the workaround was the "exotic particle" that had whatever properties the plot needed. Since, for the most part, it only showed up in a single episode, no conflicts.
Regarding B5, J Michael Straczynski was asked "How fast is travel through hyperspace?". His reply: "As fast as the plot needs".
BEWARE: B5 Spoiler Alerts!
Because JMS developed the entire five year story arc, JMS was able to fully develop the canon before shooting frame 1 of the pilot. Thus, far fewer canon violations. Two years into the series, B5 viewers were [pleasantly] shocked when the true identity of Valen was revealed. But, this identity was given away, heavily disguised, in the pilot movie.
This was done deliberately for major themes throughout the series. JMS has said [something like] "I'll lay my cards on the table beforehand. No surprises. But, you won't see it then because it's done in a disguised way and you don't [yet] have the context"
The main violations of B5 canon were due to actors wanting out of the series and rewriting so that plot points of their characters were given to other characters. Oh, let's not forget that B5 was slated to be cut short after season 4.
The epic space battle/war that appeared near the end of season 4 was originally planned to spill over into at least 1/3 of season 5, but was cut short. B5 was given a reprieve, but, by then, the "war" was over. Season 5 had to have some other subplots stretched out to compensate. The series finale episode ("Sleeping in Light") was shot near the end of season 4 and would have been the end of season 4. When the series was extended, they had to scramble to write/shoot an alternate season 4 last episode and save "Sleeping in Light" for the end of season 5.
One example of actors leaving and rewriting the arc [some of this is conjecture on my part]:
Eventually, the story arc needed a "super" telepath. In the pilot, the B5 telepath was "Lyta Alexander", played by Patricia Tallman. She was in the pilot, but did not start the series. For the early episodes, there was another telepath "Talia Winters", played by Andrea Thompson. Talia was given enhanced telepathic powers by her ex lover [who became an omnipotent super being]. These powers gradually began to grow in the series.
Later on, it became apparent the station had a mole [probably a telepath] that had a code name "Control". At this point, Andrea wants out of the series. So, they brought back Patricia's "Lyta" character and she exposes "Talia" as the mole. Andrea/Talia is now gone. Now, Lyta is the B5 resident telepath [and her "super" telepath powers were given to her during a pilgrimage she made to the Vorlons].
One characteristic of "Control" was this was a second personality implanted by the Psy Corp. The person's normal personality was unaware of this, but the artificial mole personality was aware of everything [would only come out at night when the natural personality was sleeping].
If Andrea hadn't wanted out of the series, it was more likely that the mole was Ivanova [who had mild telepathic powers]. The reason is, because "Control" had access to things that probably only a command deck officer had access to. Talia would have [eventually] exposed her. Talia would have used her extra powers to purge Ivanova's "mole" personality, thus, allowing the Ivanova character to continue. Further, if Ivanova had been the mole, the "Control" subplot/subarc could have been extended beyond the few episodes it was in.