The only thing QW really added over vanilla "netquake" was client side movement prediction. Hitscan weapons (infinite velocity bullets) only let you know if you had hit or missed based on the response from the server. You had to lead your shots a certain amount based on your current latency in order to hit your target.
It was great though. It meant you could bunny hop around corners at extremely high speeds without running into walls.
Hm, I think the engineering story is the interesting aspect:
What an elegant client-as-terminal I have for this incredibly popular physics simulation! Oh no! it takes up too much bandwidth. Welp - time to throw out the old lock-step game-loop architecture, and allow each client to stream incremental updates
I'm sure many contemporary engineers had similar problems, and considered the same approach, but either shrank-from or gave-up on rustling together an elegant solution. Like many problems in the early days of 3d/internet gaming, Carmack seems to have rapidly and nicely solved it with imagination & experimentation, all informed by a broad and deep understanding of data structures, & algorithms, and presumably an industry-leading amount of experience.
You say "only", but for those of us who's ping on a good day was between 250-300ms, it was miraculous. It is interesting though, how lag compensation on one particular aspect of the game can make such a big difference, even though the lag is still there in full force in other (just as critical) aspects of the game.
Even to this day playing from Australia it's not uncommon to have a 250-300ms ping on US/EU servers (depending on the game may be the closest English servers).
There are some changes in the movement physics which might not be obvious. QW is more forgiving wrt bunnyhopping as you can gain momentum more easily compared to NQ. The speedrunners still use NQ afaik because it is the original single player game.
It was great though. It meant you could bunny hop around corners at extremely high speeds without running into walls.