Weird FPS cap issue

[Redon]

Thanks for the responses so far.

I'm aware that this game is very old and that there might be compatibility issues with modern machines and expectations. However, I used to play Discovery online on the same PC with the same OS with no such issues before, which tells me this problem doesn't need to exist. If it wasn't possible to run this game at more than 100fps, then there would be no need for the FPS limiter in the first place.
I understand that preventing jittering is the reason the FPS limiter exists; I'm not asking to play with an uncapped frame rate. I'm trying to run the game at a smooth 120fps (with or without Vsync), which my computer is clearly capable of because it runs it at a constant 180fps offline when uncapped.

As I stated in the OP, I've tried running the game both with and without the -noframelimit option, and it made no difference. According to the FPS limiter's documentation, it is supposed to cap the frame rate at 155fps. Yet with or without -noframelimit, I get 180fps while playing offline, and with or without -noframelimit, my frame rate is capped at 100fps as soon as I connect to the server. There is no obvious reason why this should happen, and yet it does. It's not Vsync doing that, it's not frame drops due to performance issues, and it's not the 155fps cap that the FPS limiter claims to enforce.

Is the FPS limiter supposed to have an effect while playing offline? If yes, how come it does not cap my frame rate while playing offline? If no, which means it only applies once connected to the server, is there any possibility that this issue is related to the FPS limiter not working as intended, seeing as it only happens once I connect to the server?