The highly unusual choice of words might indeed suggest that. And mirror Scotty's "simple impulse power" that in a certain TOS adventure allowed a ship to travel at apparent warp speeds. Timo Saloniemi
In regards to "Balance of Terror" and Scotty saying "Their power is simple impulse" it might be that 1) "Impulse power" as Scotty refers to it might've meant simply that their faster than light drive was powered by fusion reactors that we now know is what powers the sublight drives of Federation starships. 2) Scotty was simply mistaken. Unlikely as I'm sure he could monitor the radiation emissions from the Romulan ship to tell that they were using nuclear fusion reactors rather than antimatter reactors to power their ship.
Drawing from the episode itself, I would presume the Bird of Prey utilized a low-power, high-efficiency fusion powered warp drive. As a stealthy incursion vessel and sneak-attack instrument, such a design makes a kind of sense. The warp drive and the cloak operated in tandem draw most of the power from the ship's reactors, and when the ship attacks it drops out of warp to power its weaponry, and then decloaks when it's ready to fire, which fits with the dialog and the narrative as shown. There's never a surplus of energy, and everything is "by the numbers" and fuel/resources are strictly accounted for, that the Enterprise and her crew mucked up the Romulan mission is more due to a lack of information about their enemy, than inept handling of their vessel on the part of the crew of the Praetor's Pride. Anyhow that's my two cents and I'm sticking to it. Lol.
For what it's worth, in the Star Fleet Battles (game) universe, a ship without Warp Drive can achieve some degree of Warp/FTL speed using the Impulse engines only, but not in a combat setting. How else do you think the Romulans could control a stellar empire?? Ships without warp engines must fight at sub-light speeds, which is how the First Federation-Romulan War was fought. Steve Cole calls this impulse-driven FTL mode "Non-Tactical Warp", which predates Tactical Warp (and thus begs the question of what was it called before Tactical Warp was invented??).
In theory, in FASA's game, if you had a powerful enough impulse engine, you could likely get to warp as well. But most impulse drives were not all that powerful. But the drives on say Excelsior or a Galaxy-class starship would probably have the power to movement rating needed to get the ship up to low warp speeds (if I remember the system correctly).
I would think that it is more unlikely for a starship to accidentally run into another than two planes running into each other here on earth. The addition of the third dimension vs naval ships makes it even harder for a collision to occur.
Starfleet Command 3 also allows a ship to hit warp 1 with impulse. You have to rig a super light Nebula hull by using only light systems, armed only with mines and maybe one light phaser. Most people thought I was cheating, but I used the normal in-game ship editor. I would think it would be called non-strategic warp, because low warp (below warp 2) would have the most use in an interplanetary role (~40 min from Earth to Jupiter at the speed of light, instead of weeks or months), as apposed to an interstellar role. Sleeper ships get around that. Apparently this idea of very low warp speeds being common within the human span of space history made it into TNG with how the Enterprise intercepts a Klingon sleeper ship from a time humans are known of, and Worf has to act as captain to avert a pointless battle. Obviously this concept is dropped in ENT.
Timo said: In TOS the budget usually didn't permit showing enemy ships, so they were described as being so far away they were mere dots or totally unseen. In "The Changeling" they are attacked by an unknown enemy. In The Enterprise Incident the Enterprise is being chased by a Romulan vessel. So it looks like optimum range for the Romulan main batteries would be about fifty thousand to seventy five thousand kilometers. In "Elaan of Troyius" a Klingon ship rushes at the the Enterprise. In "Journey to Babel" an unidentified ship attacks. In the TOS movies they had a bigger budget and showed ships fighting at much closer ranges. They did that again in the era of TNG. We might suppose that in the era of the TOS movies new shield designs were hundreds or thousands of times more powerful than earlier ones and so ships had to get within a few kilometers to have any chance of blasting through shields and damaging enemy ships. No doubts weapons were later greatly improved and space battles were again fought at distances of tens or hundreds of thousands of kilometers. Then by the era of TNG and DS9 shield technology improved again and ships had to get within a few kilometers in order to penetrate enemy shields and damage enemy ships.