At least with AMD drivers, you can limit to whatever framerate with whatever refresh rate, so you could get 60 FPS on a 240+ Hz monitor. Or you set your monitor to 60 Hz via windows/linux settings before starting the stream. IMO someone who knows the engine well should do extensive tests to see of there is a significant difference like with older GTAs, and after that we could discuss actual pros and cons of going with no frame limit.

I am not familiar with the source code of the engine, or how it works in detail, but over a decade ago I got very familiar with an engine that locked physics to framerate while modding (oblivion), and have basic understanding of coding after wasting multiple years on a computer science degree. Looking back at GTA 3 and VC, that also used renderware, just with less modifications, higher framerate could make a difference, since some things are locked to framerate. The game engine is broken as it is IMO (unless you use Windows XP), so unlocking framerate could have side effects. Sure, there are ways around it like with SA Limit Adjuster, but seeing how even GInput is not allowed, I doubt that ASI loader + Limit Adjuster would get a free pass all of sudden.

TLDR: unlocking FPS would be like opening Pandora's box, especially since you'd have to use modifications that are currently forbidden, if you want to keep it consistent for everyone. I personally like it when SA runs with 60 fps fixed, casually, or even 75 since my monitor supports it, but it's a different topic.You wouldn't speedrun Skyrim with 144 FPS either, since it's locked to a max of 60 FPS and beyond that game physics are just a suggestion, not a rule. But maybe someone intimately familiar with SA implementation of Renderware can cover that one better.